US3189882A

US3189882A - Alarm system with synchronous scanning

Info

Publication number: US3189882A
Application number: US110191A
Authority: US
Inventors: Emmett J Ward
Original assignee: Westinghouse Electric Corp
Current assignee: Westinghouse Electric Corp
Priority date: 1961-05-15
Filing date: 1961-05-15
Publication date: 1965-06-15
Anticipated expiration: 1982-06-15

Description

June 15, 1965 E. J. WARD 3,139,882

5 Sheets-Shea?l l NIL June 15, 1965 E. J. WARD ALARM SYSTEM WITH SYNCHRONOUS SGANNING 5A Sheets-Sheet :21

Filed May l5, 1961 June l5, 1965 E. J. WARD 3,189,882

ALARM SYSTEM WITH SYNCHRONOUS SCANNING Filed May 15, 1961 5 sheets-sheet s N www Hw W 7H NQ SNES ,EN Q E @www w www .f mmm SN V.n l

June 15, 1965 E. J. WARD ALARM SYSTEM WITH SYNCHRONOUS SCANNING 5 Sheets-Sheet 4 Filed May 15. 1961 June 15, 1965 E. J. WARD ALARM SYSTEM WITH SYNGHRONOUS SCANNING 5 Sheets-Sheet 5 Filed May 15, 1961 United States Patent O w sasassa apartar srsrnitr wrrn srncrrnosrops scannen-1;

Emmett it. Ward, Sylmar, Caii., assigner, by mesne assignments, to Westinghonse Electric Corporation, a corporation of Fennsylvania Filed May i5, INTL, Ser. No. lithw 17 Ciaims. (Cl. 34h-M3) This invention relates to an alarm system and more particularly to an improved system for providing central control of industrial security requirements.

In many industrial plants, and particularly in those plants having a number of separate buildings, it has become desirable to provide some means for centrally control-ling the security requirements of the entire plant. Since the security requirements for an .industrial plant may take a number of diiferent forms, the security alarm system may be called upon to perform many diiferent functions. Accordingly the security alarm system may be required to provide means for centrally monitoring the pressure or temperature in buildings remote from the central location, or it may be required that the system provide central control for detecting intrusion violations within `the remote buildings. In addition to providing central control of the many security requirements of an industrial plant the security :alarm system should utilize a minimum of circuitry interconnecting the remote building locations with the central locations, thereby maintaining cabling expenses at a minimum. Further, since it is generally desired that a minimum of personnel be required to maintain `the security requirements of the industrial plant the alarm system should be highly reliable and substantially automatic in its operation.

In view of the above, the present invention provides a security alarm system wherein a plurality of remote area stations, which may be remote building locations, are each connected to a central control center by a single pair of wires. To provide detection of any violation of plant security requirements there are positioned at each remote station a plurality of detection elements. These detection elements yare constructed to sense alarm conditions and operate upon any change in, or violation ot, the security requirements set by the industrial plant. At each remote area station there is further provided a detection module to interconnect each detection element with the single pair of wires leading to the central control center. In accordance with the present invention, the detection module functions to automatically generate a pulse signal indicative of the alarm condition sensed by each of the operated detection elements. This signal is electrically transmittcd over the single pair of wires to the central control center thereby providing central indication of all alarm conditions.

Accordingly the present invention provides an alarm system which .in addition to satisfying the security requirernents of an industrial plant requires a minimum of circuitry between remote area stations and the central control center and is completely automatic in its operation.

More particularly, in a preferred embodiment of the present invention, the detection module located at each of the remote area stations includes a novel combination of relay circuitry and a stepping switch. In accordance with the present invention this combination operates to determine the particular detection element or elements which have operated and to generate pulses indicative of the alarm condition sensed by t-he operation of each of the detection elements. in particular each detection element is connected by a closed loop to a Contact of the stepping switch. Means are provided which upon operation of a detection element within the remote area station energizes the stepping switch, such that it hunts for the con- ICC tact associated with the operated detection element. Upon `finding an operated detection element the stepping switch becomes deenergized thereby ceasing to hunt. Means are .further provided in the detection module for generating a pulse for each step in the hunting operation of the stepping switch. This pulse signal is the signal indicative of the alarm condition sensed by an operated detection element which is transmitted to the central control center.

Further, in the preferred embodiment of the present invention, the central control center includes for each remote area station a central stepping switch which oper ates in synchronism with the stepping switch located at an associated remote area station. Still further, the central control center includes means common to all central stepping switches for indicating and/ or recording the operation of a detection element at any one of the remote area stations. Upon indication of an operated detection element means are provided at the central control center for transmitting a signal to the remote area station associated with the operated detection element to reenergize the remote station stepping switch. Thus the remote station stepping switch can continue its hunting operation. if no other detection elements have operated the remote station stepping switch returns to a home position and is deenergized, readying the stepping switch for a new hunting operation in the event of an alarm condition at another detection element. Since the associated stepping switch at the central control center operates in synchronism with the remote area stepping switch it also returns to a home position.

lt is a feature of the present invention that means are provided at the central control center for insuring synchronism between the stepping switches located at the central control center and the stepping switches located at the associated remote area stations. In the preferred embodiment of the present invention this is accomplished by providing means for motorizing each central stepping switch to its home position each time the stepping switch located at its associated remote area station returns to its home position.

A more complete understanding of the above, as well as other features of the present invention, may be had by reference to the following detailed description when considered in connection with the drawings in which:

FIG. l is a block diagram of the security alarm system of the present invention;

FIG. 2 is a block diagram depicting the relationship between FIGS. `3, 4 and 6;

4FIGS. 3 and 4 are a schematic diagram of the circuitry of a remote area station;

FIG. 5 is a timing diagram representing the operation of the relays illustrated in FIGS. 3 and 4; and

FIG. 6 is a schematic diagram of the circuitry of the central control center associated with `a remote area station.

eferring to FIG. l, there is shown a block diagram of the security alarm system of the present invention. As shown, a central control center 2d provides means for interconnecting a plurality of remote area stations (Nos. 1 through N) each by a single pair of wires. As represented, there is associated with each remoted area station a plurality of detection units. In particular, Area No. i is shown to include detection units 1 through n. As will Ybe described in detail in connection with FIGS. 3 and 4, a change in, or violation of, the security requirement determined by these detection units produces a pulse signal at the remote area station which is indicative of the particular detection unit that has been operated. The pulse signal is transmitted over a pair of wires to the centrai control center 29. As will be described in detail in connection with FIG. 6, the pulse signal received from a remote areas station is indicated or recorded at the central control center 20, thereby providing means for centrally determining the particular detection unit which has been operated. When this occurs an operator at the central control center may initiate central control over the alarm condiion represented by the operation of the detection element.

In considering the circuitry and operation of a remote area station, reference should be made to FIGS. 3 and 4 in combination with FIG. 5. FIGS. 3 and 4 represent the circuitry for a remote area station in accordance with a preferred embodiment of the present invention. As described brielly above, the circuitry of the remote area station provides means for interconnecting a plurality of detection elements to the pair of wires which extend between the remote area station and the central control center. In general, the circuitry of the remote area station provides means for developing pulse signals indicative of the operation of particular detection elements. Accordingly, when a detection element operates, circuitry is energized which detects the particular detection element which has operated and generates a pulse signal indicative of the particular detection element. This pulse signal is then transmitted over the two-wire connection to the central control center.

More particularly, as shown in FIGS. 3 and 4, the circuitry of the remote area station includes a plurality of detection units Nos. 1 through n. As represented each detection unit is connected to a contact point of a stepping switch, which by way of example is illustrated as being a stepping rotary switch 22. As will be described in detail below, upon operation of a detection element, stepping rotary switch 22 functions in combination with a novel relay arrangement to hunt for and generate a pulse signal indicative of the operated detection element.

As is further illustrated in FIGS. 3 and 4, the relay arrangement associated with stepping rotary switch 22 includes a combination of

relays

24, 26, 28, 30, 32, 34, 36 and 38. As will be explained in greater detail below, relay 24 controls the operation of stepping rotary switch 22 and produces a pulse signal for each step operation ofV stepping rotary switch 22. Relays 26, 28 and 30, which may be termed operate-time control means control the period of time over which relay 24 is in an operative condition. Relays 32, 34 and 36 which may be termed release-tirne control means, control the period of time over which relay 24 is in a release condition and provide means for maintaining the release of relay 24 when stepping rotary switch 22 detects an operated detection element. Relay 38 provides means for transmitting the pulse signals over the two-wire path between the remote area station and the central control center.

Specically as shown, each detection unit includes similar circuitry. Accordingly, only the circuitry associated with detection unit No. 1 will be described in detail and like reference numerals having a subscript denoting the particular detection unit will apply to like elements of the other detection units. As shown, detection unit No. 1 includes a detection element 40. Detection element 46 may take a variety of forms depending upon the condition to be detected. For example, the detection element may be a pressure sensitive transducer which opens a circuit associated therewith when the pressure being monitored exceeds a safe level. The detection element may be a temperature sensitive transducer which breaks a circuit when the temperature exceeds a safe limit. The detection element may comprise a continuous conductor such as commonly used metal tape on windows for indicating a breaking and entering situation. Although the detection element may take a number of different forms it should include some form of switching means, such as indicated at 41. As shown switch 41 is normally closed to provide a current path. However detection element 40 is so arranged as to operate switch 41 when an alarm condition is sensed. More particularly, as shown in FIG. 3, one terminal of the switch 41 is connected to ground by a resistor 42 and the other terminal is connected to a winding 44 of a detection unit relay 46. As shown winding 44 is connected in common with a second winding 4S of relay 46 through a resistor 50 to a battery 52. Winding 48 of relay 46 is also connected through a variable resistor 54 to ground. In practicing the present invention the value of resistor 54 is varied such that with detection element 4t) in its normally inactivated state with switch 4i closed, equal current ilows from battery 52 through resistors 42 and 54 thereby maintaining relay 46 in a released condition.

As represented by dotted line 55, relay 46 operates a plurality of

switches

56, 58 and 60. When the relay 46 is released, switch 56 provides an open circuit connection for a lamp 62, switch 58 provides an open circuit connection connected to winding 48 of relay 46 and switch 60 provides a ground connection to a contact point of the stepping rotary switch 22.

In the actuated state of the relay 46, switch 56 connects ground to the lamp 62 thereby allowing current from a battery 64 to ignite the lamp 62. The lighting of the lamp 62 provides a visual indication of an alarm condition at the associated remote area station. Switch 5S, when closed, connects ground through the resistor 54 to a timing circuit indicated generally at 65, which will later be described in detail. The switch 60 operates to remove ground from the contact point of the stepping rotary switch 22 which is associated with detection unit No. 1 and connects ground to a contact point 68, which, as will be described below, deiines a home position for the stepping rotary switch 22.

As described above each detection unit is associated with a particular contact point of stepping rotary switch 22. In particular each detection unit is coupled by its switch 66 to an associated contact point of the stepping rotary switch 22. For convenience each contact point of the stepping rotary switch 22 will be denoted by the number of its associated detection unit. Accordingly contact point 1 will be associated with detection unit No. 1 and contact point n will be associated with detection unit No. n. As shown in FIGS. 3 and 4, the stepping rotary switch 22 includes a wiper arm 66 that is positioned to initially impinge upon a contact point 68 which defines a home position for wiper arm 66. By home position is meant that after completion of its stepping operation, the stepping rotary switch 22 will automatically advance the wiper arm 66 to the Contact 68 and then deenergize, waiting for the operation of another detection element.

As represented in FIGS. 3 and 4, stepping rotary switch 22 further includes a relay 70 having a winding 72. One end of the winding 72 is connected to a battery 76. T he other end of the winding is connected by a capacitor to ground and to a switch S2 oper-ated by relay 24. As will be described in detail in connection with the relay 24, the operation of switch 82 causes relay 76 to energize. When energized relay 7G is so constructed as to set a spring assembly (not shown) associated with stepping rotary switch 22 such that when relay 70 releases wiper arm 66 is stepped one contact point. Stepping switches of this type are well known. The operation of relay 24, by causing switch 82 to close, controls the operation of stepiping rotary switch 22. Thus each time relay 24 operates and releases, the wiper arm 66 is stepped one contact point.

As represented in FIGS. 3 and 4, the relay 24 includes a winding $3. As shown winding 83 includes a terminal S4 which is connected to a battery S5 and a terminal 86 which is coupled to a series capacitor-resistor circuit 37 to ground. Termin-al 86 is also connected through a switch 88 of relay 30 and a switch 90 of relay 36 to the wiper arm 66 of stepping rotary switch 22. Accordingly, when a ground condition appears at the wiper arm 66, current, ilows from battery to operate relay 24.

i3 The relay 24 controls a plurality of switches S2, 2 9d and 96. With the relay 24tin a released co-..

switches

2, 92, 943 are as represented in FlG. 3 Thus the switch S2 provides an open condition to winding 72 of relay 7@ thereby maintaining the release ot relay 7?. Switch 92 connects a capacitor from ground to a normally open switch of the relay So and to an open contact of a switch 161 of the relay Sil. Switch @Il connects a capacitor to ground through a resistor 1li-dthereby maintaining thc capacitor 1&2 in a discharged state. The switch 96 normally connects ground to relay 33.

With relay `2d in an operated condition, switches 32, 92, gt4 and 96 are actuated. Accordingly switch S2 connects winding 72 of relay 7@ to ground thereby allowing current to flow from the battery '76 to energize the stepping rotary switch 22. The switch 92 connects capacitor $3 to a resistor 1%. Since the resistor 1% is connected to ground, this causes the capacitor 98 to discharge. rthe switch connects relay 3S to a battery 11E-3. As will be described in detail later, operation of the switch 96 produces a pulse signal indicative of the position of the stepping rotary switch 22, which signal may be transmitted to the central control center. ln an operated condition, the switch 94 connects discharged capacitor 1512 to terminal 111@ of winding 112 of relay 26 thereby initiating the operation of the operate-time control means o' the present invention.

As previously mentioned, the `operate-time control means includes

relays

26, 28 and Si? which function to control the period of time over which the relay 24 is in an operative condition. Thus upon the operation of relay 2d the operate-time control means functions to cause relay to release after a period of time which is determfned by the operate-time control means. The release of relay 24 allows the wiper arm 66 of the stepping rotary switch 22 to step one contact point. As will hereinafter be described in detail the operation of the operate-time control means to cause the release of relay Z4 also initiates the operation of the release-time control means. ously mentioned the release-time control means includes relays 32, 361 and 3o which function to control the period of time over which relay 2d remains in a released condition. Thus after a period ol time determined by the release-time control means, relay 2d is allowed to operate. However, as will be discussed in detail, should the wiper arm 66 be impinging upon a contact point which is associated with an operated detection element, the relay 2&2 remains in a released condition.

Referring to the operate-time control means as represented in FIGS, 3 and 4, terminal 1li/"l of winding 1.12 of relay 26 is connected to a battery 1.1 Thus, the operation of the switch 94- of relay 24 allows current from battery 116 to pass through the winding 112, causing relay 26 to operate for a period of time required for capacitor 1612 to reach a charged condition through the resistance of the winding 112. Operation of the relay 25 closes its normally open switch 118 thereby connecting ground through a switch 12b of relay Si? to terminal of winding 124 of relay Z3. As represented, relay 2S includes two windings, 124 and 126. As shown terminal 12S of winding 17d and terminal 139 of winding 12:6 are connected in common to one side of a battery 132. Terminal of 134 of winding 126 is connected to a normally open switch 13d which, together with a switch operates in response to the operation of relay 23.

As represented in FIGS. l3i and 4, `with relay 28 in a released condition switch 136 connects an open circuit condition to switch 12d of relay and switch 13S connects an open circuit condition to terminal 1 of a winding Wit-h relay 23 in an operated condition switches and 13S connect the terminal 134tto switch and ground to terminal 14d, respectively. Ars shown, a terminal 144i of winding 141-2 is also connected to terminal of winding 124.

As previ- Y As shown in FGS. 3 and 4, relay 3? includes two windings, 142 and 14o, winding 145 having terminals 14S and 15?. Terminal is connected to a battery 152 and terminal 1S@ is connected to the switch 12). As represented by dotted line 154, the operation ot relay 3G controls the operation of switches 1111, 123i? and 88, the position of each with relay 39 in a released condition being as previously described. With relay 3? in an operated condition, switch 126 connects the circuit condition present at switch of relay to switch 136 of relay 2S, and to terminal ot winding ldd on relay 30. Switch 88 disconnects wiper arm 66 from winding 83 of relay 24 thereby causing relay 24 to release, Accordingly the period over which relay 24 remained in an operated condition is controlled by the operation of

relays

26, 28 and 3G.

The operation of relay Sil also causes switch 101 to connect ground through discharged capacitor 98 and through now released switch 12 of relay 24 to a terminal 156 of a winding 1552 of relay 32 thereby initiating the operation of the release-time control means of the present invent-ion. As sho-wn the circuitry associated with the release-time control means is substantially similiar to that associated with the operate-time control means. Accordingly, a terminal 1o@ of winding 15 is connected .to a battery 162. Thus the operation of switch 161 permits current from battery 152 to operate relay 32 for a period of time determined b the time constant of winding 158 and capacitor Operation of relay 32 closes normally open switch 164 thereby connecting ground through a switch 166 of relay 3o to terminal of winding 17d of relay 34. As represented, relay includes two windings, 17@ and 172. Terminal 17d of winding 17d and terminal 176 of winding 172 are connected in common to one side of a battery 178. Terminal of winding 172 is connected to a normally open switch 132 which, together with a switch 184, operates in response to the operation of relay 34. As represented in FlGS. 3 and 4, with relay 34 in a released condition, switch 182 provides an open circuit condition to the switch 16o of relay 36 and the switch 184 provides an open circuit condition to a terminal 186 of a winding 183 of relay 36. With relay 34 in an operated condition, switches 182 and 1d@ connect the terminal 189 to switch 166 and ground to terminal 136. As shown a terminal of winding 13B is also connected to the terminal 153 of winding 170.

As illustrated in l lGS. 3 and 4, relay 3o includes two windings 18d and 1%, winding 192 having terminals 194 and 19a. Terminal 194 is connected to a battery 198 and terminal 1% is connected to the switch 16o. As represented by dotted line Zilli, the operation of relay 36 controls the operation of switches 1%, 166 and 91D, the position or each with relay 3o in a released condition be- ,ing as previously described. With relay 36 in an operated condition, the switch 166 connects the circuit condition present at switch 164 of relay 32 to switch 132 of relay 34 and to terminal 196 of winding 192 of relay 36. Switch 1% connects the circuit condition present at switch of relay to the switch lol of relay 3G. Switch 9i) reconnects wiper arm to winding S3 of relay 24 thereby allowing relay 24 to again operate in response to a ground condition present at wiper arm 66. Accordingly, the period of time over which relay 2.4i remains in a released condition is controlled by the operation of

relays

32, 3d and 36.

Considering the operation of the circuitry thus far described to detect the operation ot a detection element and to transmit a pulse signal indicative of the operated detection element, reference should be made to FIGS. 3 and 4 in combination with FIG. 5. Assume that detection element of detection unit No. operates. This caused switch 4114= to operate which places an open circuit condition upon winding of relay 464 thereby unbalancing relay 464 and causing it to operate. The operati-on of relay 464 closes switch 564 causing light 624 to light, indicating an alarm condition to personnel at the remote area station. The operation of relay 46., also operates switch 6114 thereby providing an open circuit condition on contact point 4 of stepping rotary switch 22. The operation of switch 604 also places a ground condition on contact point 63 of stepping rotary switch 22. This ground condition is applied to the terminal 86 of winding 83 of relay 24 through switch 96 of relay 36 and switch 88 of relay 30. This causes relay 24 to operate thereby operating switches 82, 92, 91tand 96. Thus at a time r1 as represented in FIG. 5 relay 24 has operated.

As previously mentioned the closing of switch S2 (at t1) in response to operation of relay 24 energizes relay 7@ of stepping rotary switch 22. The energizing of relay 70 primes stepping rotary switch 22 such that upon the release of relay '7o the wiper arm 66 is caused to step from contact point 68 to contact point No. 1. As previously mentioned, the operation of switch 96 results in a pulse signal being transmitted to the central control center. Since a pulse is transmitted upon each operation of relay 24, the number of pulses in the pulse signal acts as an indication of the operated detection element (in this instance 404).

The operation of switch 94 at t1 connects discharged capacitor 162 to winding 112 of relay 26. Accordingly current will liow from battery 116 through winding 112 to operate relay 26 for a period of time determined by the time constant of winding 112 and capacitor 102. As previously mention-ed, the operation of switch 94 initiates the operation of the operate-time control means of the present invention. Accordingly, after a period of time relay 24 is caused to release. in particular, the opera- Ition of relay 26 closes switch 118 at t2 thereby extending ground through switch 126 of relay it@ to winding 124 of relay 23. The closing of switch 113 at t2 provides a current path from battery 132 through winding 124 thereby causing relay 2S to operate. The operation of relay 28 closes switch 138 thereby connecting ground to terminal 144i of winding 142. The operation of relay 28 also closes switch 136. Upon charging of capacitor 1112 relay 26 releases. Accordingly, at t3 (as represented in FG. 5) switch 118 opens thereby removing the ground from terminal 122 of winding 12d. This provides a current path from battery 132 through winding 124 and winding 142 of relay 30 to ground at switch 133 of relay 23. The flow of current from battery 132 will cause relay 3% to operate. The operation of relay 311 at I., will operate switches 101, 12@ and 8S. The operation of switch 3S will disconnect wiper arm 66 from winding 33 of relay 24. Accordingly as represented in FIG. 5 relay 24 then releases, com-pleting the operation of the operate-time control means.

The release of relay 24 causes switches $2, S2, 94 and 96 to also release at t5. The release of switch 82 causes relay 70 to deenergize thereby causing wiper arm 66 to step from contact point 63 to contact point No. 1. The release of switch 92 connects discharged capacitor 98 to switches 161 and 1011 of relays 3@ and 36 respectively. The release of switch 94 connects charged capacitor 162 to ground through resistor 1114i thereby causing capacitor 162 to discharge.

As previously mentioned the operation of relay 316 at t4 causes switch 1111 to operate. The operation of switch 101 connects discharged capacitor 93 to winding 15S of relay 32. As previously mentioned, this initiates the operation of the release-time control means of the present invention. Accordingly, after -a period of time wiper arm 66 is reconnected to winding S3 of relay 24 thereby allowing relay 24?. to operate in response to a ground condition present at wiper arm 66. In particular the connection of capacitor 98 to relay 32 causes current to tlow from battery 162 through winding 156 thereby causing relay 32 to operate at t6. Relay 32 is energized for a period of time determined by the time constant of its winding 158 and capacitor 93. The operation of relay 32 at t6 extends ground from now closed switch 164 to the winding 171i' of relay 34. This provides a current path from battery 178 through winding 176 of relay 34 thereby causing relay 34 to operate. The operation of relay 34 extends ground from switch 164 to terminal 186 of winding 1S?, thereby maintaining relay 36 in a released condition. The operation of relay 34 also causes switch 132 to operate.

Upon the charging of capacitor 98, relay 32 releases. The resulting opening of s-witch 164 at tf1 removes ground from the terminal 16S of winding 170. Thus a current path now extends from the battery 178 through the winding 170 of relay 34, through the winding 188 of relay 36 to ground at the switch 184 of relay 34. This flow of current unbalances relay 36 thereby causing it to operate. The ope-ration of relay 36 at t8 causes switches 100, 166 and to operate. The operation of switch 90 again connects the Wiper arm 66 through the switch 90 and the switch 86 of relay 36 to the winding 83 of relay 24. Since a ground condition exists at the wiper arm 66, relay 24 again operates. Accordingly, the release-time control means of the present invention has controlled the period of time over which relay 241 remained in a released condition.

The operation of relay 24 at t8 again causes switches S2, 92, 94 and 96 to operate. Thus with relay 24 fully operated at t9, the switch 82 again energizes relay 70 as to set stepping rotary switch 22. The operation of the switch 92 connects the capacitor 9S to ground through the resistor 166, thereby allowing the capaci-tor 98 to discharge. Closing of the switch 94 connects the discharged capacitor 162 to the winding 112 of relay 26. As previously described this causes relay 26 to operate at tm thereby again initiating the operation of t-he operate-time control means.

As represented in FIGS. 3 and 4 the operation of the relay 26 extends ground through the switch 113 to

relays

28 and 30. As represented in FIG. 5, at this point in time, however, relay 36 is still operative. Thus at tm the ground extends from the switch 118 through the operated switch 121D, the closed switch 136 of relay 28 to the winding 126. This allows current to flow from the battery 132 through the winding 126 thereby balancing relay 28 and causing it to release.

At tm the ground connection from the switch 118 also extends to the winding 146 of relay 30. Accordingly current may iow from the battery 152 through the winding 146 thereby maintaining relay 30 in an operative condition even though the release of relay 23 causes the switch 138 to disconnect ground from the winding 142 of relay Sil.

As indicated at tn in FIG. 5 upon the charging of the capacitor 102, relay 26 is released. The release of relay 26 removes ground at the switch 113 from the winding 1626 of relay 30. This again balances relay 36 causing it to release. The release of relay 30 at i12 in turn causes switches 8S, 121B and 161 to release. The release of switch 88 at i12 again removes a ground condition present at the wiper arrn 66 of stepping rotary switch 22 from winding 33 of relay 24 thereby causing relay 24 to release at tw.

The release of relay 24 again causes a release of

switches

82, 92, 94 and 96. The release of switch 82 deenergizes relay 71B thereby causing wiper arm 66 to step to contact point No. 2. The release of the switch 94 connects the capacitor 162 to ground through the resistor 1194 thereby allowing the capacitor 102 to discharge. Release of the switch 92 at tu connects the capacitor 98 through the closed switch 160 of relay 36 and through the switch 101 of relay 31D to the winding 15S of relay 32, thereby causing relay 32 to again become operative. rThis causes the release-time control to again become op erative.

As represented in FiGS. 3 and 4 the completed operaaieasse tion of relay 32 at im connects ground through the switch 26d, operated switch 166 of relay 36, through the operated switch E82 of relay to the winding 172 of relay 34. The connection of ground to the winding 172 of relay 34 allows current to tlow from the battery through the winding 272 thereby balancing relay 34, causing it to release. The ground condition at switch E64 is also connected to the winding 192 of relay Thus current iiows from the battery 19S through the winding 92, maintaining relay 36 in an operated condition even though the release of relay 34 removes ground at the switch from the winding 188 of relay 36. As indicated at 135 in PEG. 5, upon the charging of the capacitor 92 associated with relay 24, relay 32 releases. The release of relay 32 removes ground irorn the winding 192 of relay 35 thereby causing relay 36 to release. The release of relay 36 at Ile in turn causes the switch 9d to release, again connecting ground from the wiper arm 66 of the stepping rotary switch 22 through the switch 9@ and the switch 83 of relay 30 to the winding 83 of the relay 24. This ground connection causes relay 24 to operate again.

Since an open condition exists at contact d oi stepping rotary switch 22, the above operation 4is repeated, that is, relay 24 twice operates, positioning the wiper arm 66 of the stepping rotary switch 22 at contact No. li.. Relays 26, 2S, 3d, 32, 34 and 36 also operate as previously described to control the periods of times for which relay 2d is operative and released. As represented in FiG. 5, at the point of time when the wiper arm 66 irnpinges upon contact 4, relays 26, 28 and 3? are in a released condition. After a period of time relays 32, 34 and 36 operate and release, thereby again connecting the wiper arm 66 to the winding 33 of relay 24. Accordingly at this time the open circuit condition which exists at contact point d extends through the switch 90 of relay 36, the switch S8 of relay Sii, to the winding S3 ot relay 24. This open circuit condition maintains relay 24 in a deenergized state. Also during this period of time, by operation of the switch 96 of relay 24, four pulses have in eliect been transmitted to relay 33 and hence over a two-wire transmission path 202 to the central control center. In transmitting these pulses, relay 38 remains inoperative. This inoperative condition is due to the differential winding and balance of relay 38. in particular, by adjusting the value of a resistor 204 which is connected to winding 206 of relay 3S the current from battery 108 hows equally through the winding 2% to ground and through a winding 298 of relay 38 to the two-wire transmission path 2h52. Since equal currents iiow through the two windings of relay 38, relay 38 remains in a balanced condition and therefore is not operated.

From the above it is seen that in response to the operation of the detection element 494, the detection module represented in FIGS. 3 and 4 has caused its stepping rotary switch 22 to step four contact positions and to generate a pulsed signal having a corresponding number oi pulses that is indicative of the particular detection element which has been operated. Further, from the above it is seen that the operation of the stepping rotary switch 22 has been controlled by relay 24. Still further the operation and release of relay 2d has been controlled by the operate-time control means (including relays 26, 2S and 30) and the release-time control means (including relays 32, 34 and 36). in particular it may be noted from FIG. 5 that relay 2d controls each operation and release of

relays

28 and 30. More specifically relay 2S operates and releases in response to consecutive operations of relay 26, Further relay Si) operates and releases in response to consecutive releases of relay 26. in a like manner it may be noted that relay 32 controls the operation and release of relays 3d and 36.

As will be described in detail in connection with FG. 6, the pulses transmitted to the central control center energize circuitry providing an indication of the particular detection element which has been operated. Upon occurrence of this indication, a signal is generated at the central control center which is transmitted over transmission path 2B2 and received by relay 38. This signal unbalances relay 3d and causes it to operate. The operation of relay closes the switches 2i@ and 2i2. The closing of switch 2li@ connects ground to the winding 83 of relay thereby energizing relay 2d. The operation of relay 2dthen proceeds as described above, causing the wiper arm 66 of stepping rotary switch 22 to step from point contact to point contact in search of another operated detection element. Upon linding another operated detection element, relay 243- is deenergized until a signal is received from the central control center indicating that the central control center has received and recognized the operated detection element. Upon receipt of this signal from the central control center, relay 24 is reenergized, causing stepping rotary switch 22 to continue its hunting operation. It stepping rotary switch 22 finds no other operated detection elements, it returns to its home position at contact point 63 where it is deenergized by an open condition at Contact 53.

The operation of relay 3S in response to the signal from the central control center also closes the switch 212. The closing of the switch 212 connects ground to a timing circuit. The timing circuit comprises

relays

214 and 216 and switches associated therewith. The timing circuit turther includes a motor M which drives timing cams 217 and 2id. It is a purpose of the timing circuit to cause the regeneration at periodic intervals of puise signals indicative of the previously operated detection elements for transmission to the central control center to insure an indication of the operated detection elements. it is a further purpose of the timing circuit to provide means for automatically deenergizing detection unit relays associated with operated detection elements which have been placed in an inactivated state with switch 41 in a closed condition.

As previously mentioned the operation of relay 3S applies a ground to winding 21S ot relay 214. A current path is then provided from a battery 220 through the winding 2id to ground. rl'he iiow of current causes the relay 2id to operate thereby operating

switches

222, 224, 22d and 228. The operation of switch 222 connects winding 2318 of relay 2id to ground at a contact 230 associated with the timing cam 217. This ground connection maintains relay 224 in an operative condition. The closing of switches 226 and 223 connects ground at the switch 226 to the switch 58 of each of the detection units and removes a ground connection formerly connected to the switch 53 at the contact 23@ or timing cam 217. As will be described in detail below, this provides means for deenergizing detection unit relays associated with detection elements which have been placed in an inactivated state. The operation of switch 224 of relay 224 places a ground condition upon the winding 232 of relay 216. ribis provides a current path from a battery 234 through the winding 232 to ground. The flow of current causes relay 2li@ to operate.

The operation of relay 226 causes switches 236, 233, and 2d@ to operate. The closing of switch M .me connects the winding 232 of relay 2id to ground through the resistor-capacitor series combination 242. The operation or" switch 236 disconnects the homing position contact 68 of stepping rotary switch 22 from switch 6i? of all detection units. The operation of switch 24@ connects ground to motor M thereby starting motor M. As illustrated by dotted line 244, timing cams 2M and 218 are mechanically coupled to motor M. As represented by arrows 246 and 243 the operation of motor M causes timing cams 217 and 2id to rotate in a clockwise direction. After a period of time, which is determined by the rotation speed of timing cam 2718, Contact 25@ falls into a slot 252. As represented by spring 25d, contact 2550 is tensioned such that when contact 256 falls into slot 252, switch 236 of relay 2id again closes a circuit between switch 60 of each detection unit and the home position contact point 68 of stepping rotary switch 22. By way of example only, the time required for timing cam 218 to rotate into a position such that contact 256 drops into slot 252, may be fifteen seconds. The closing of switch 236 connects home contact point 68 to ground if any detection element has been operated. Since due to the signal from the central control center stepping rotary switch 22 will have completed its hunting operation and will have returned to its home position, the appearance of a ground condition at contact point 68 energizes stepping rotary switch 22, causing it to hunt for the operated detection element. The operation of stepping rotary switch 22 causes a pulse signal to be transmitted to the central control center indicative of each of the particular detection elements which are now operated. Thus since the detection elements which caused the prior operation of the alarm system will still be operated, a pulse signal indicative of such operation is again transmitted to the central control center. These pulse signals reinitiate circuitry at the central control center to again indicate that the particular detection ele ments are in an operated condition.

As timing cam 218 continues its rotation, it causes contact 250 to release from slot 252 thereby opening switch 236 of relay 216. After another period of time determined by the rotational speed of timing cam 218, contact 250 drops into slot 256. In so doing it again operates switch 236 of relay 216 thereby repeating the process previously described. As a result a pulse signal is again transmitted to the central control center indicative of the operated detection elements at the remote area station. Accordingly it is seen that the operation of the timing circuit causes pulse signals indicative of operated detection elements to be twice repeated to insure indication at the central control center.

When contact 250 drops into slot 256, contact 258 associated with timing cam 217, drops into slot 268. This disconnects ground at contact 238 from the winding 218 of relay 214, causing relay 214 to release. The release of relay 2214 causes

switches

222, 224, 226 and 228 to also release. The release of switch 224 removes ground from winding 232 of relay 216. However, due to the prior operation of relay 216 the winding 232 is also connected to ground through resistor-capacitor series combination 242. Accordingly relay 216 remains operative for a period of time determined by the time constant of circuit 242 and winding 232 of relay 216. The operation of switches 226 and 228 removes ground from the switch 58 of all detection units. Accordingly any previously operated detection unit relays which have had their associated detection units placed in an inactivated condition with switch 41 closed are allowed to deenergize. This is due to equal currents now owing through

windings

44 and 48 of detection unit relay 46. The period of time for which an open circuit condition is connected to switch 58 of relay 46 is determined by the time which Contact 258 is in slot 26! of timing cam 217.

As previously mentioned since the winding 232 of relay 2K6 is connected to ground through the resistor-capacitor circuit 242, relay 216 is maintained in an operative condition until the capacitor of circuit 242 reaches a charged condition. When this occurs, relay 226 deenergizes, releasing

switches

236, 238 and 240. Release of the switch 236 again connects the home position contact 68 of stepping rotary switch 22 to the switch 60 of all detection units. The release of switch 240 removes ground from motor M thereby halting its operation.

Accordingly, from the above, it is seen that the timing circuit has provided means for repeating pulse signals associated with operated detection elements, has provided means for transmitting these repeat signals to the central control center to insure indication of the operated detection elements at the central control center, and has provided means for automatically deenergizing detection unit relays associated with detection elements which have l2 been placed in an inactivated condition ready to sense other alarm conditions.

From the above description of FIGS. 3 and 4, it is seen that upon operation of a detection element at one of the detection units, a series of pulses is generated indicative of the particular detection element. The pulse signal is then transmitted to the central control center where it initiates circuitry to provide an indication of the operation of the detection element. Upon such indication, signal is transmitted back to the remote area station to reenergize circuitry which reinstitutes the search for other operated detection elements.

Referring now to FIG. 6 there is represented circuitry of the central control center associated with each remote area station. As previously mentioned, this circuitry functions to provide means for indicating the operation of particular detection elements at each remote area station and, upon such indication, transmitting a signal to the remote area station associated with the operated detection element to reinstitute the search by circuitry at the remote area station for other operated detection elements. To accomplish this, the central center includes for each remote area station a pulse receiving relay for receiving pulse signals from the remote area station, a central stepping switch operative in response to pulses received from the remote area station, and indicator or recording means and its associated circuitry for providing an indication of the particular detection element which has been operated. The indicator or recording means of the central control center may take a number of forms. For example, such means might include a printer for permanently recording the operation of detection elements, an indicator panel having a light positioned lfor each detection element in the remote area stations, and/or audible alarm circuitry. By way of example only, the indicator or recording means of the central control center is illustrated in FIG. 6 as lbeing an indicator panel having a light position for each detection element associated with each remote area station.

Referring specifically to FIG. 6, there is shown a pulse receiving relay 262 connected to receive pulses from a remote area station. Relay 262 is represented as having two

windings

264 and 266. The winding 264 includes

terminals

268 and 270. Terminal 268 is connected to transmission path 202 and terminal 270 is connected in common with a terminal 272 of winding 266 through a normally open switch 344 controlled by an indicator relay 274 to a battery 346. The remaining terminal 276 of winding 266 is connected to ground through a variable resistor 278. By adjusting the value of the resistor 278, relay 262 may be balanced such that signals applied to the common terminals 270 and 272 of

windings

264 and 266 respectively, will not energize relay 262.

Pulse signals from a remote area station being received at terminal 268 unbalance relay 262 thereby causing it to operate. Accordingly relay 262 operates in response to each pulse received from a remote station. As shown in FIG. 6, associated with relay 262 are normally

open switches

280 and 282.

Switches

280 and 282 operate when relay 262 is energized thereby connecting ground to an indicator control relay 284 and to a relay 236 associated with a central stepping rotary switch 288. As will be described in detail below, ground applied from

switches

280 and 282 respectively, causes relays 284 and 286 to operate.

As represented by dotted line 290, indicator control relay 284 controls the operation of switches 292 and 294. With relay 284 in a deenergized state the switch 292 connects ground to a resistor-capacitor circuit 295, causing capacitor 296 of circuit 295 to discharge. When relay 284 is energized switch 292 connects circuit 295 to winding 298 of relay 284 thereby providing a means for maintaining relay 284 in an operated condition after ground is removed from the winding 298 by the release of switch 280 associated with relay 262. In particular,

sassarese relay 28d remains operated for a period of time determined by the time required for current from a battery 299 to charge capacitor 296. With relay 234 energized, switch 294 also operates. Switch 294 when operated connects ground to terminal 300 of a winding 392 of transformer 304. As shown, terminal 366 of winding 302 is connected to a battery 36S. Accordingly with switch 294 in its operative condition current tlows through winding 302. As further represented, transformer 364 includes a secondary winding 310. As shown secondary winding 310 has two terminals 312 and 314, terminal 312 being connected to a capacitor 316 and terminal 324 connected by a diode 318 to a wiper arm 326 associated with stepping rotary switch 288. As will be described in detail below, it is the function of indicator control relay 284 and its associated circuitry to provide means for energizing the light position of an indicator panel 322 after stepping rotary switch 28S has recognized the particular detection element which has been operated at the remote area station. Accordingly indicator control relay 234 and its associated circuitry provides means for applying a signal to wiper arm 320 after it has reached a contact point associated with the operated detection element.

As previously mentioned, the central control center includes a central stepping rotary switch for each remote area station. As will be described in detail below, a central stepping rotary switch is operated by pulses received from the associated remote area station to step in synchronism with the stepping rotary switch located at the remote area station. Accordingly by providing the central stepping rotary switch with a plurality of contact points, each point corresponding in representation to the contact points of the stepping rotary switch located at the remote area station, the position of the wiper arm associated with the central stepping rotary switch indicates the particular detection element which has been operated at the remote area station.

More particularly, as shown in FIG. 6, stepping rotary switch 283 includes wiper arm 32d and a plurality of contact points. These contact points are given the same designation as those of the stepping rotary switch at the associated remote area station. As is further illustrated, central stepping rotary switch 283 includes relay 286 and associated

switches

324 and 326. As will be described in detail below, relay 286 operates to produce the stepping of stepping rotary 286. In particular when relay 286 is energized, stepping rotary switch 28d is placed in a set condition. When relay 236 is deenergized wiper arm 320 is caused to step from one contact point to the next. As is shown, winding 328 of relay 236 is connected to switch 282 of relay 262. Accordingly each time, relay 262 is operated, ground at switch 232 is applied to winding 328 of relay 286. In this condition current ilows from a battery 329 through winding 323 of relay 286 to ground thereby energizing relay 286. Since switch 232 operates each time relay 262 is energized by a pulse received from a remote area station, relay 236 also energizes in response to each pulse from an associated remote area station. Accordingly for each pulse received from a remote area station wiper arm 320 steps one Contact position. ln stepping, wiper arm 320 impinges upon consecutive contact points. As represented each of these contact points connects to a particular light position of an indicator panel 322 thereby providing means for centrally indicating the operation of all detection elements located at the associated remote area stations.

As represented in FlG. 6, each light position of indicator panel 322 includes a neon tube 330 having

terminals

332 and 334. As shown, terminal 332 of neon tube 33t? is connected to ground through a resistor 336, while terminal 334 of neon tube 33t) is connected to a battery 338. Due to the characteristics of neon tube 331i, current only ows through neon tube 330 after a threshold potential associated therewith has been exceeded. However, after wiper arm 320 reaches a contact point indicative of an operated indication element, a voltage signal is applied across a resistor 340 which is combination with the potential of battery 338 exceeds the threshold potential of neon tube 33H3. Thus in response to the detection of the operative detection element by stepping rotary switch 23S, a particular neon tube of indicator panel 322 is operated thereby providing a visual indication to an attendant at the central control center of the alarm condition which has been sensed by the operated detection element.

As represented in FIG. 6, each group of light positions associated with a remote area station is coupled to indicator relay 274. As shown, winding 342 of indicator relay 274 is connected to terminal 332 of neon tube 33t?. Accordingly, current is only applied to winding 342 of relay 274 after neon tube 330 has been ignited. Current flowing through winding 342 operates relay 274 thereby closing switch 344 associated with relay 274. The closing of switch 344 applies a current signal from a battery 346 to the common connection of

windings

264 and 266 of relay 262. Due to the aforementioned balanced condition of relay 262, this signal does not energize relay 262 and is transmitted to the remote area station. Accordingly, after a light position has been ignited at indicator panel 322, a signal is generated which is transmitted to the remote area station associated with the operated detection element. This signal is utilized, as previously described, in connection with FIGS. 3 and 4 to reenergize relay 24 such that stepping rotary switch 22 may hunt for other operated detection elements or may return to its home position.

In seeking out other operated detection elements pulse signals are transmitted from the remote area station to the central control center. Accordingly, the central `stepping rotary switch 288 continues to step in synchronisrn with the stepping rotary switch located at its associated remote area station. Thus when the stepping rotary switch of the remote area station recognizes the operation of another detection element, a light condition is produced at the central control center corresponding to the particular detection element which has been operated. Further, if the stepping rotary switch located at the remote area station should rind no other `operated detection element the central stepping rotary switch stepping in synchronism with its associated remote area stepping rotary switch returns to its home position. However, should a pulse from the remote area station be lost in transmission it is desirable to provide means for insuring a stepping synchronism between the remote area station stepping rotary switch and the central stepping rotary switch. Accordingly, a self-.synchronizing circuit is provided in combination with the central stepping rotary switch.

As shown in FIG. 6, the synchronizing circuit includes a thermal relay 348. Thermal relay 348 is shown t0 include a switch 350 and heating element 352 having

terminals

354 and 356. As shown, terminal 351i of heating element 352 is connected to a battery 35S while terminal 356 is connected through a resistor 363 to switch 324 of relay 236. As is further shown in FIG. 6 switch 35@ is also coupled to switch 324. If a pulse has been lost in transmission between the remote area station and the central control center, when the stepping rotary switch of the remote area station returns to its home position, the central stepping rotary switch will be positioned at a Contact point other than the home contact position 63'. With the central stepping rotary switch ofi its home position, switch 324 is so constructed as to be operated. The operation of switch 324 provides a current path from battery 358 through heating element 352 to ground. Current liowing through heating element 352 causes switch 35i) to operate after a period of time determined by the construction of thermal relay 34S. By way of example only, this period of time may be ninety seconds. rent now flows from battery 329 .through winding 32S of relay 286, through switches 326 and 354i to ground at switch 324. Relay 286 is constructed that such current ow motorizes stepping rotary switch 288. Stepping rotary switch 288 being motorized will then drive wiper arm 328 to its home contact position at contact 68 thereby insuring synchronism between stepping rotary switches located at the remote area location and the central control center.

Consider now the overall operation of the circuitry shown in FIG. 6 in response to the four pulses received from the remote area station shown in FIGS. 3 and 4. Pulses from the remote area station are received by receiving relay 262 which energizes and deenergizes in response to each pulse. Accordingly, switch 282 operates and releases four times. The operation of switch 282 causes relay 286 to energize and deenergize four times. This in turn causes wiper arm 320 of stepping rotary switch 288 to Istep four positions. At this point in time wiper arm 320 is impinging upon contact No. 4' thereby connecting the light position associated with contact 4 to the indicator control relay circuitry.

In response to the four pulses received by relay 262 switch 280 will have operated four times. Upon the first operation of switch 280, relay 284 is energized thereby operating switches 292 and 294. As previously described the operation of switch 294 produces a current flow in winding 302. However, due to diode 318, current is prevented from ilowing in winding 310. After receiving the four pulses from the remote area station, relay 262 becomes deenergized thereby releasing switch 280. As previously mentioned relay 284 then remains operated for a period of time determined by the time constant of circuit 295 and winding 298 of relay 284. When capacitor 296 of circuit 295 becomes charged, relay 284 deenergizes thereby releasing switch 294. The release of switch 294 causes a surge of current in winding 310 through diode 318 to contact No. 4. This surge of current is applied to indicator panel 322 by resistor 340. The surge of current causes the threshold voltage of neon tube 330 to be exceeded thereby causing neon tube 330 to light. The potential of battery 33S is now suflicient to maintain neon tube 330 in a lighted condition. This lighted condition remains until an attendant at the central location extinguishes it by opening a switch 362 which is connected in series with neon tube 33t). As represented in FIG, 6, with neon tube 330 in a lighted condition current owing through neon tube 330 is applied to winding 342 of relay 274. Relay 274 then operates to generate a signal from battery 346 lwhich is transmitted by relay 262 to the remote area station associated with the operated detection element. This signal, as previously described, is utilized to reinstitute a search at the remote area station for other operated detection elements.

Considering FIGS. 3, 4 and 6 in combination it is to be understood that in addition for providing means for automatically detecting changes in, or violations of, security requirements determined by detection elements at their associated remote location, the present invention also provides means whereby the central control center may communicate with any remote area station independent of the alarm circuitry heretofore described. This communication may be accomplished by transmission over a pair of wires 202 between the central control center and any remote area station. Over these pairs of wires an attendant at the central control center may send command signals to the remote area stations which will initiate circuitry to control various security functions at the remote area stations or he may utilize these transmission paths to communicate directly with personnel at the remote area stations.

From the above detailed description it is seen that the present invention provides a security alarm system for centrally controlling security requirement at a plurality of remote area stations. This central control is provided over a single pair of wires between each remote area station .and the central control center thereby maintaining cable expense at a minimum. Further the present invention provides an alarm system whereby changes in, or violations of, security requirements at remote area stations are automatically detected at a central location thereby maintaining plant security personnel at a minimum. Finally, from the above detailed description, it is seen that the present invention provides an alarm system which requires a minimum of circuitry to accurately and reliably detect changes in or violations of security requirements of an industrial plant.

What is claimed is:

1. In a security alarm system which comprises a central control center and a plurality of remote stations each being connected to said control center by a single pair of wires, said remote station having a plurality of detection elements operable for sensing particular alarm conditions and means for transmitting pulse signals indicative of the operation of said detection elements to said central control center, the combination comprising at said central control center: means for receiving said pulse signals from said remote stations; a plurality of stepping switches, one associated with each remote station and each including a wiper arm and a plurality of contact points, each of said contact points denoting a particular detection element at the associated remote station; means responsive to each pulse received from said remote stations for energizing an associated stepping switch, such that the switch steps one contact point for each pulse received; indicator means connected to said contact points of said stepping switches for providing a particular indication for each operated detection element, said indicator means including means for only providing an indication when a wiper arm of a stepping switch impinges upon a ycontact point associated Iwith an operated detection element; and means responsive to an indication of an operated detection element at said indicator means for generating a signal to the remote station associated with said operated detection element, said signal being indicative of the reception by said indicator means of the alarm condition represented by the operation of said detection element.

2. A security alarm system comprising: a plurality of remote stations, each station including a plurality of detection elements operable for sensing particular alarm conditions, a remote station stepping switch having a wiper arm and a plurality of contact points, a separate contact point being connected to each detection element, means responsive to the operation of a detection element for energizing said stepping switch, such that said wiper arm steps in Search of the contact point associated with said operated detection element, means for deenergizing said stepping switch when said wiper arm impinges upon the contact point associated with said operated detection element, means for generating a pulse signal for each step of said wiper arm of said remote station stepping switch, a pair of wires, and means for transmitting said pulse signals over said pair of wires; and a central control center connected to each of said remote stations by the pair of wires associated with each remote station, said central control center including for each remote station means for receiving each of said pulse signals from the associated remote station, a central stepping switch, said central stepping switch including a wiper arm and a plurality of contact points, each of said contact points denoting a particular detection element at the associated remote station, means for energizing said central stepping switch in response to each pulse signal from the associated remote station such that said wiper arm of said central stepping switch steps in synchronism with said wiper arm of the associated remote station stepping switch, indicator means connected to said contact points of said central stepping switch for providing a particular indication of the operation of said operated detection element at said associated remote station, and means responsive to such indication by said indicator means for generating a signal to `the associated remote aisassa station, said signal reenergizing said remote station stepping switch thereby allowing its wiper arm to step in search of other operated detection elements.

3. A security alarm system as deiined in claim 2 Wherein said central control center includes means for resynchronizing said central stepping switch with said associated remote station stepping switch, the last-named means including relay means for generating a signal when said central stepping switch is out of synchrcnism with said associated remote station stepping switch, and means responsive to such signal for operating said central stepping switch into synchronism with said associated remote station stepping switch.

d. ln a security alarm system comprising a central control center and a plurality of remote stations, each being connected to said central control center by a single pair of wires, and each remote station having a plurality of detection elements which are operated in response to particular alarm conditions, the combination comprising at each remote station: a remote station stepping switch having a wiper arm and a plurality of contact points, a separate contact point being connected to each detection element; means responsive to the operation of a detection element for operating said stepping switch such that said wiper arm steps in search of the Contact point associated with said operated detection element; means, in circuit with said last-named contact point, for Stopp ig said stepping switch to maintain said wiper arm in en agement with the last-named contact point when said wiper arm impingcs upon said last-named contact point; ns for generating a pulse signal for each step of said wiper arm and means for transmitting said pulse signal over the associated pair of wires to said central control center.

ln a security alarm system comprising a central control center and a plurality of remote stations, each being connected to said central control center by a singl pair of wires, and each remote station having a plurality of detection elements operable for sensing particular alarm conditirms7 the combination comprising at each rernote station: a remote station stepping switch having wiper arm and a plurality of contact points, a sepcontact por, being connected to ea h detection clement; means responsive to the operation of a detection element for operating said stepping switch such that wiper arm steps in Search of the contact point associated with said operated detection element; means, in circuit with said last-named contact point, for stopping said stepping switch to maintain said wiper arm in enwith the last-named contact point when said wiper arm ir es `pon said last-named contact point;

f. y.rmg means lor transmitting said pulse signal over the associated pair of wires to said central control center s responsive to reception by said control center lse signal associated with the stepping of said i to the contact point associated with said opdetection element for automatically rendering said switch operative to step said wiper arm in search lerated detection element.

n which comprises a central of remote stations, each staed to central control center by a i remote station having a plurality of elements operable for sensing particular alarm ons, the combination comprising at each remote g "ng switch including a Wiper arm and a plu- Contact points, a separate contact point ocing with each of said detection elements such that -ctiori element is represented at its asnt by a first condition and such that tact tection clem-ents, said Wiper arm initially inipinging upon said one contact point; relay means connected to said stepping switch at said wiper ar said relay means operating in response to said lrst cond ion and releasing in response to said second condition; means responsive to the operation of said relay means for energizing s id stepping switch, such that said wiper arm of said stepping switch steps one contact point upon the release of said relay means; means responsive the operation ot a detection element for eff 'ng said lirst condition at said one conthereby energiz'ng said relay means causing re ay means to operate; operate-time control means .d to said relay means responsive to the operation of said relay means for causing said relay means to release alter a hrst predetermined period of time by disconnecting said relay means from said wiper arin, thereby causing said wi er arm 'to step one contact point; releasetime control means cf :pled to said relay means responsive to the operation of said operate-time control means for reconnecting relay means to said wiper arm after a second predeter ed period of time following said iirst period thereby allow -v'd relay means to reoperate in response to said first condition appear ng at said wiper arm; means coupled to said relay means for generating a pulse signal in response to each operation of said relay means; and means for transmitting said pulse signal over the asso ted pair ot wires to said central control center.

"1'. fr detection system comprising in combination: a plnrality of detection elernent"; a stepping switch including a winer arm and a plnr y of contact points, a separate contact point being associated with each of said deelements such that an unoperated detection elcrnent is represente, at its associated Contact point by a irst condition and such that an operated detection element is reprn ed at its associated contact point by a second condition, one or said contact points being connected in common to of said detection elements, said wiser arm initially implnging upon said one contact point; relay means connected to said stepping switch at said wioer arn said relay means operating in response to said first condition and releasing in response to said second condition; means responsive to the operation of said relay means for e c* i s wiper arm will step one contact point upon the rese of said relay means; means responsive to the operaof a detection element for effecting s id lirst condition at said one contact point thereby energ ng said relay .leans causing said relay means to operate; operate-time control means coupid to said relay means, said operatetime control means inclu 7ng a first operate-time control relay, a first capacitor, means responsive to each operation of said relay means for coup g said lirst capacitor to said iii-st t e control relay such that said first ate-tir operate-time control re ay will operate for a period of time determined by said first capacitor upon each operation oi said relay a second operate-time control relay coupled to said first operate-time control relay, n cans coupled to said first operate-time control relay for n and releasing said second operate-time control relay in csponse to consecutive operations of said first operatee control relay, a third operate-time control relay coupled to said second operate-time control relay, coupled to said first operate-time control relay for operating and releasinfy said third operate-time control relay in response to consecutive releases of said first operato-time control relay and means responsive to each operation and release of said third operate-time control relay for disconnecting said wiper arm from said relay thereby causing said relay nicans to release; release-time control means coupled to said relay means, said release-time control means including a rst releasetime control relay, second capacitor, .eans responsive to each operation of said relay means for coupling said second capacitor to said tir-st release-time control relay such that said first release-time control relay will operate for a period of time determined by said second capacitor l@ for each release of said relay means, a second release-time control relay coupled to said rst release-time control relay, means coupled to said first release-time control relay for operating and releasing said second release-time control relay in response to consecutive operations of said lirst release-time control relay, a third release-time control relay coupled to said second release-time control relay, means coupled to said first release-time control relay for operating and releasing said third release-time control relay in response to consecutive releases of said rst release-time control relay, and means responsive to each operation and release of said third release-time control relay for connecting said wiper arm to said relay means thereby allowing said relay means to reoperate; means coupled to said relay means for generating a pulse signal in respouse to each operation of said relay means; and means for utilizing said pulse signal.

S. A security alarm system comprising a plurality of remote stations each including: a plurality of detection elements operable for sensing particular alarm conditions, a remote station stepping switch including a wiper arm and a plurality of contact points disposed for successive engagement by said wiper arm, said stepping switch being set with said wiper at a starting contact point, a separate Contact point being coupled to each detection element of the associated remote station, relay means coupled to said remote station stepping switch, means responsive to operation of one of the associated detection elements for cycling said relay means to render said relay means alternately energized for a first predetermined period of time and deenergized for a second predetermined period of time, means responsive to each cycle of operation of said relay means for stepping said wiper arm from each of said contact points to the next successive one of said contact points in search of the contact point coupled to said operated detection element, means in circuit with said last-named point connected to said relay means for stopping the cycling of said relay means on the arrival of said wiper at said lastnarned point, means for generating a separate pulse signal for a predetermined portion of each cycle of operation of said relay means; and a central control center including for each remote station: means for receiving each pulse signal generated at the associated remote station, a central stepping switch including a wiper arm and a plurality ot` contact points disposed to be successively engaged by such wiper arm, each of such contact points denoting a particular detection element at said associated remote station in the same sequence as said detection elements are coupled to said associated remote station stepping switch Contact points, means responsive to each pulse signal received from said associated remote station for stepping the corresponding central station wiper arm in synchronism with the wiper arm of said associated remote station, and indicator means coupled to the Contact points associated with said corresponding central station wiper arm responsive to engagement of such wiper arm with the contact point corresponding to the remote station contact point coupled to said operated detection element for providing a particular indication of the operation thereof.

9. A security alarm system comprising a plurality of remote stations each including: a plurality of detection elements operable for sensing particular alarm conditions, 4a remote station stepping switch including a wiper arm and a plurality of contact points disposed for successive engagement by said wiper arm, a separate contact point being coupled to each detection element of the associated remote station, relay means coupled to said remote station stepping switch, means responsive to operation of one of the associated detection elements for cycling said relay means to render said relay means alternately energized for a first predetermined period of time and deenergized for a second predetermined period of time, means responsive to each cycle of operation of said relay means for stepping said wiper arm from each of said contact points to the next successive one of 'said contact points in search of the contact point coupled to said operated detection element, means for delaying the further cycling of said relay means and thereby the further stepping of said wiper arm in response to engagement of said wiper arm with the contact point coupled to said operated detection element, means :for generating a separate pulse signal for a predetermined portion of each cycle of operation of said relay means; and a central control center including for each remote station: means for receiving each pulse signal generated at the associated remote station, a central stepping switch including a wiper arm and .a plurality of Contact points disposed to be successively engaged by such wiper arm, each of .such contact points denoting a particular detection element at said associated remote station in the same sequence as said detection elements are coupled to said associated remote station stepping switch contact points, means responsive to each pulse signal received from said associated remote station for stepping the corresponding central station wiper arm in synchronism with the wiper arm of said associated remote station, indicator means coupled to the contact points associated with said corresponding central station wiper arm responsive to engagement of such wiper arm with the contact point corresponding .to the remote station contact point coupled to said operated detection elements for providing a particular indication of the operation thereof, and means responsive to such indication for generating a pulse signal; means for receiving such pulse signal at said associated remote station, and means responsive to the reception of such pulse signal by such remote station for terminating said delay of the further cycling of its relay means and thereby of the further stepping of its wiper arm.

llt). A secunity alarm system comprising a plurality of Iremote stations each including: a plurality of detection elements operable for sensing particular alarm conditions, a remote station stepping switch includ-ing a wiper arm and a plurality of contact points disposed for successive engagement by said wiper arm, a separate contact point being coupled to each detection element ot the associated remote station, relay means coupled to said remote station stepping switch, means responsive to operation of one of the associated detection elements for cycling said relay means to render said relay means alternately energized for a irst predetermined period of time and deener* gized for a .second predetermined period of time, means responsive to each cycle of operation of said relay means for stepping said wiper arm from each of said contact points to the next successive one of said contact points in Search of the contact point coupled to said operated detection element, means for delaying the further cycling of said relay means and thereby the further stepping of said wiper arm in response to engagement of said wiper arm with the contact point coupled to said operated detection element, means for generating a separate pulse signal for a predetermined portion of each cycle of operation of said relay means; and a central control center including for each remote station: means for receiving each pulse signal generated at the associated remote station, a central stepping switch including a Wiper arm and a plurality of contact points disposed to be successively engaged by such wiper arm, each of such contact points denoting a particular detection element at said associated remote station in the same sequence as said detection elements are conpled to said associated remote station stepping switch contact point-s, means responsive to each pulse signal received from said associa-ted remote station for stepping the corresponding central station wiper ar-m in synchronism with the wiper arm 4of said associated remote station, indicator means coupled to the contact points associated with said corresponding central station wiper arm responsive to engagement of such wiper arm with the contact point corresponding to the remote station contact point coupled to said operate-d detection clement for providing a particular indication of the operation thereof, and means responsive sigterminating said delay of means and thereby of tbe further stepping of its wiper arm, and additional means responsive to sncn reception for eiecting reinstitution of tbe search of sncli wiper arm to Verity tbe operation of said operated detection element.

lll. ln a 4security alarm system comprising a central control center and a plurality of remote stations eacli being connected to said central control center by a single pair of wires and eacb remote station liaving a plurality of detection elements operable for sensing particular alarm conditions, the coi bination comprising at each remote station: a remote station st ping switch including a wiper arm and a plnr I of Contact points disposed tor successive engagement by said wiper arm, a separate Contact point being coupled to each detection element of the associated remote station, relay means coupled to said remote station stepping switch, means respo'- sive to operation of one ot the associated detection elem-nts for cycling said relay means t lender said relay means alternately energized for a predetermined period of time deenergized for a second predetermined period of time, means Aresponsive to eacli cycle of operation of said relay means for .stepping said wiper arm from each of said Contact points to the next successive one of said contact points in Search ot the contact point coupled to said operated detection element, means in circuit Wit'n said last-named point connected to said relay means for stopping the cycling of said relay means on the arrival of said Wiper at last-named point, means for generating a separate e lgnal for predetermined por .on of each cycle of ation ot said relay means, and means for transmitting of said pulse signals over tbe associated pair of Wires aid central con l center.

A security al rm system comprising a remote station navin(y a plurality or detection elements each operable for sensing a particular alarm condition, remote station stepping means coupled to eacli of said detection elements operable for searching said detection elements in a predeteri .ed sequence, means responsive to operation of one of said detection elements for operating said remote station stepping means to step from each detection element to the next successive one of said detection elements in Search of said operated detection element, timing means coupled to said remote station stepping means for effecting each step or such stepping means only at the expiration of a predetermined interval of time following tiro preceding step ot' snob st raping means, means circuit with said operated detecting element for stopping tbe operation of said remote-station stepping means on the arrival of said stepping means at said operated detection element, and means for generating pulse signal separately from said stepping means during a predetermined portion of each of said intervals of time; and a central station including inicator means for each of said detection elements operable for providing a particular indication of the operation of such detection element, central station stepping means coupled to each or said indicator means operable for searching said indicator means in the same sequence as said remote station stepping means is operable for searching said detection elements, means for receiving eacli of said pulse signals ge rated at said remote station, means responsive to each pince signal received from said remote station for operatinf7 said central station stepping means to step in synchronism with said remote station stepping means, and means responsive to the stepping of said c-entral station stepring means to tbe indicator means associated with said operated detection element for Jersting suoli indicator means.

i3. A security alarm system comprising a remote station having a plurality of detection elements each operable for sensing a particolar alarm condition, remote station .T22 ming means coupled to each of said detection elements c aole for searching said detection elements in a predetermined sequence, means responsive to opera-tion of one of said detection elements for operating said remote station stepping means to step from each detection element to tbe next successive one of said detection elements in Search of said operated detection element, means for delaying tile further stepping of said remote station stepping means in response to the stepping tliereorP to said operated detection element, timing means coupled to said remote station stepping means for effecting each step of such stepping means only at tire expiration of a predetermined interval of time following the preceding step of such stepping means, and means for generating a separate pulse signal during a predetermined portion of each or said intervals or" time; and a central station including indicator means for each or detection elements operable for providing a particular indication of the operation of such detection element, central station stepping means coupled to each oi said indicator means operable for searching said indicator means in tbe same sequence as said remote station stepping means is operable for searching said detection elements, means for receiving each of said pulse signals generated at said remote station, means responsive to each pulse signal received from said remote station for operating said central station stepping means to step in synchronism with said remote station stepping means, means responsive to tne stepping of said central station stepping means to the indicator means associated with said operated detection element for operating such indicator means, and means responsive to operation of the last-named indica-tor means for generating a signal; means for receiving such signal at said remote station, and means responsive to re Y)tion of sncn signal by said remote station for tern ating said delay of the further stepping of said remote station stepping means.

le. A security alarm system comprising a remote station having a plurality of detection elements each operable `for sensing a particular alarm condition, remote station Steppinfr means coupled to each of said detection elements operable for searching said detection elements in a predetermined sequence, means responsive to operation or one of said detection elements for operating said remote station stepping means to step from each detection element to tbe next successive one of said detection elements in search of said operated detection element, means for delaying 'tire nrtlier stepping of said remote station stepping means in response to the stepping thereof to said operated desection element, timing means coupled to said remote station stepping means for effecting each step of such stepping means only at the expiration ot a first predetermined interval or time following the preceding step of sucli step ng means, and means for generating a separate pulse signal during a predetermined portion of each of said rst intervals of time; and a central station including indicator means for each of said detection elements operable for providing a particular indication of tbe operation of stcli detection element, central station stepping means coupled to each of said indicator means operable g said indicator means in tbe same sequence as said remote station stepping means is operable for searching said detection elements, means for receiving each of said pulse signals generated at said remote station, means responsive to each pulse signal received from said remote station for operating said central station stepping neans to step in synclironism with said remote station stepping means, means for delaying operation of tne indicator means associated with each step of said central station stepping means for a second predetermined interval of time following the stepping of said central station stepping means to the last-named indicator means, said second interval being greater than said rst interval, means responsive to expiration of said second interval following tire stepping or" said central station stepping means to the indicator means associated with said operated detection element for operating such indicator means, and means responsive to operation `of the last-named indicator means for generating a signal; means for receiving such signal at said remote station, and means responsive to reception of such signal by said remote station for terminating said delay of the further stepping of said remote station stepping means.

15. A security alarm system comprising a remote station having a plurality of detection elements each operable for sensing a particular alarm condition, remote station stepping means having steps each iixedly coupled to a corresponding one of said detection elements operable -for scanning said detection elements in a predetermined sequence, means spontaneously responsive to operation of one of said detection elements for operating said remote station stepping means to step from each detection element to the next successive one of said detection elements scanning said elements in search of said operated detection element, timing means coupled to said remote station stepping means for effecting each step of such stepping means during the scanning only at the expiration of a predetermined interval of time following the preceding step of such stepping means, and means for generating a separate pulse signal during a predetermined portion of each of said intervals of time; and a central station including indicator means for each of said detection elements operable for providing a particular indication of the operation of such detection element, central station stepping means coupled to each of said indicator means operable for scanning said indicator means in the same sequence as said remote station stepping means is operable for scanning said detection elements, means for receiving each of said pulse signals generated at said remote station, means responsive to each pulse signal received from said remote station for operating said central station stepping means to step in synchronism with said remote station stepping means, means responsive to the stepping of said central station stepping means to the indicator means associated with said operated detection element for operating such indicator means, and means for resync'nronizing said central station stepping means with said remote station stepping means, the last-named means comprising means for generating a signal when said central station stepping means is out of step with said remote station stepping means, and means responsive to such signal for operating said central station stepping means into step with said remote station stepping means.

16. A security alarm system comprising a remote station having a plurality of detection elements each operable for sensing a particular alarm condition, remote station stepping means coupled to each of said detection elements operable for searching said detection elements in a predetermined sequence, means responsive to operation of one of said detection elements for operating said remote station stepping means to step from each detection element to the next successive one of said detection elements in search of said operated detection element, means for delaying the further stepping of said remote station stepping means in response to the stepping thereof of said operated detection element, timing means coupled to said remote station stepping means for eiecting each step of such stepping means only at the expiration of a predetermined interval of time following the preceding step of such stepping means, and means for generating a separate pulse signal during a predetermined portion of each of said intervals of time; and a central station includingV indicator means for each of said detection elements operable for providing a particular indication of the operation of such detection element, central station stepping means coupled to each of said indicator means operable for searching said indicator means in the same sequence as said remote station stepping means is operable for searching said detection elements, means for receiving each of said pulse signals generated at said remote station, means responsive to each pulse signal received from said remote station for operating said central station stepping means to step in synchronism with said remote station stepping means, means responsive to the stepping of said central station stepping means to the indicator means associated with said operated detection element for operating such indicator means, and means responsive to operation of the last-named indicator means for generating a signal; means for receiving such signal at said remote station, means responsive to reception of such signal by said remote station for terminating said delay of the further stepping of said remote station stepping means, and additional means responsive to such reception for electing reinstitution of the search of said remote station stepping means to verify the operation of said operated detection element.

317. ln a security alarm system which comprises a central control center and a plurality of remote stations, each station ebing connected to said central control center by a pair of wires, each remote station having a plurality of etection elements operable tor sensing particular alarm conditions, the combination comprising at each remote station: a stepping switch including a Wiper arm and a plurality of contact points, a separate contact point being associated with each of said detection elements such that an unoperated detection element is represented at its associated contact point by a rst condition and such that an operated detection element is represented at its associated contact point by a second condition, one of said contact points being connected in common to all of said detection elements, said Wiper arm initially impinging upon said one contact point; relay means connected to said stepping switch at said wiper arm, said relay means operating in response to said ilrst condition and releasing in response to said second condition; means responsive to the operation of said relay means for energizing said stepping switch, such that said wiper arm of said stepping switch steps one contact point upon the release of said relay means; means responsive to the operation of a detection element for eiiecting said first condition at said one contact point thereby energizing said relay means causing said relay means to operate; operate-time control means coupled to said relay means and responsive to the operation of said relay means for causing said relay means to release after a first predetermined period of time by disconnecting said relay means from said wiper arm, thereby causing said Wiper arm to step one Contact point; said operate-time control means including a rst operatetime control relay, a lirst capacitor, means responsive to each operation of said relay means for coupling said first capacitor to said iirst operate-time control relay such that said irst operate-time control relay operates for a period of time determined by said first capacitor upon each operation of said relay means, a second operatetime control relay coupled to said iirst operate-time control relay, means coupled to said first operate-time control relay for operating and releasing said second operate-time control relay in response to consecutive operations of said iirst operate-time control relay, a third operate-time control relay coupled to said second operate-time control relay, means coupled to said first operate-time control relay for operating and releasing said third operate-time control relay in response to consecutive releases of said rst operate-time control relay and means responsive to each operation and release of said third operate-time control relay for disconnecting said Wiper arm from said relay means thereby causing said relay means to release; and wherein said release-time control means includes a iirst release-time control relay, a second capacitor, means responsive to each operation of said relay means for coupling said second capacitor to said iirst release-time control relay such that said rst release-time control relay operates for a period of time determined by said second capacitor for each release of said relay means, a second release-time control relay coupled to said rst releasealeaeea time control relay, means coupled to said rst release-time control relay for operating and releasing said second release-time control relay in response to consecutive operations of said first release-time control relay, a third release-time control relay coupled to said second releasetime control relay, means coupled to said lirst releasetime control relay for operating and releasing said third release-time control relay in response to consecutive releases of said first release-time control relay, means responsive to each operation and release of said third release-time control relay for connecting said wiper arm to Said relay means thereby allowing said relay means to reoperate, release-time control means coupled to said relay means and responsive to the operation of said Operate-time control means for reconnecting said relay means to said wiper arm after a second predetermined period of time following said rst period thereby allowing said relay means to reoperate in response to said first condition apearing at said wiper arm; means coupled to said relay means for generating a pulse signal in response to each 25 operation of said relay means; and means for transmitting said pulse signal over the associated pair of Wires to said central control center.

References lited by the Enamner UNITED STATES PATENTS NE1L C. READ, Primary Examiner.

Claims

2. A SECURITY ALARM SYSTEM COMPRISING: A PLURALITY OF REMOTE STATIONS, EACH STATION INCLUDING A PLURALITY OF DETECTION ELEMENTS OPERABLE FOR SENSING PARTICULAR ALARM CONDITIONS, A REMOTE STATION STEPPING SWITCH HAVING A WIPER ARM AND A PLURALITY OF CONTACT POINTS, A SEPARATE CONTACT POINT BEING CONNECTED TO EACH DETECTION ELEMENT, MEANS RESPONSIVE TO THE OPERATION OF A DETECTION ELEMENT FOR ENERGIZING SAID STEPPING SWITCH, SUCH THAT SAID WIPER ARM STEPS IN SEARCH OF THE CONTACT POINT ASSOCIATED WITH SAID OPERATED DETECTION ELEMENT, MEANS FOR DEENERGIZING SAID STEPPING SWITCH WHEN SAID WIPER ARM IMPINGES UPON THE CONTACT POINT ASSOCIATED WITH SAID OPERATED DETECTION ELEMENT, MEANS FOR GENERATING A PULSE SIGNAL FOR EACH STEP OF SAID WIPER ARM OF SAID REMOTE STATION STEPPING SWITCH, A PAIR OF WIRES, AND MEANS FOR TANSMITTING SAID PULSE SIGNALS OVER SAID PAIR OF WIRES; AND A CENTRAL CONTROL CENTER CONNECTED TO EACH OF SAID REMOTE STATIONS BY THE PAIR OF WIRES ASSOCIATED WITH EACH REMOTE STATION, SAID CENTRAL CONTROL CENTER INCLUDING FOR EACH REMOTE STATION MEANS FOR RECEIVING EACH OF SAID PULSE SIGNALS FROM THE ASSOCIATED REMOTE STATION, A CENTRAL STEPPING SWITCH, SAID CENTRAL STEPPING SWITCH INCLUDING A WIPER ARM AND A PLURALITY OF CONTACT POINTS, EACH OF SAID CONTACT POINTS DENOTING A PARTICULAR DETECTION ELEMENT AT THE ASSOCIATED REMOTE STATION, MEANS FOR ENERGIZING SAID CENTRAL STEPPING SWITCH IN RESPONSE TO EACH PULSE SIGNAL FROM THE ASSOCIATED REMOTE STATION SUCH THAT SAID WIPER ARM OF SAID CENTRAL STEPPING SWITCH STEPS IN SYNCHRONISM WITH SAID CENTRAL STEPPING SWITCH STEPS IN SYNCHRONISM STEPPING SWITCH, INDICATOR MEANS CONNECTED TO SAID CONTACT POINTS OF SAID CENTRAL STEPPING SWITCH FOR PROVIDING A PARTICULAR INDICATION OF THE OPERATION OF SAID OPERATED DETECTION ELEMENT AT SAID ASSOCIATED REMOTE STATION, AND MEANS RESPONSIVE TO SUCH INDICATION BY SAID INDICATOR MEANS FOR GENERATING A SIGNAL TO THE ASSOCIATED REMOTE STATION, SAID SIGNAL REENERGIZING SAID REMOTE STATION STEPPING SWITCH THEREBY ALLOWING ITS WIPER ARM TO STEP IN SEARCH OF OTHER OPERATED DETECTION ELEMENTS.