US2210621A - Electric signaling system - Google Patents

Description

Aug. 6, 1940. P. P. HORN! ELECTRIC SIGNALING SYSTEM Filed June 15 1956 4 Shgets-Sheet l BY 211M115. MM!

Aug. 6, 1940. P. P. HORN! 2,210,621

ELECTRIC SIGNALING SYSTEM Filed June 15, 1956 4 Sheets-Sheet 2 LL53 -L/ L2- 07mm Tan/sous: Y

INVENTOR. Paul P Horru' F ATTORNEYS Aug. 6, 1940. P. P. HORN! ELECTRIC SIGNALING SYSTEM Filed June 15, 1956 4 Sheets-Sheet 3 INVENTOR. Paul 1? H0272;

ATTORNEYS Aug. 6, 1940. P. P. HORN! ELECTRIC SIGNALING SYSTEM Filed June 15, 1936 4 Sheets-Sheet 4 Paul P INVENTOR. Horne ATTORNEYS- Patented Aug. 6, 1940 UNITED STATES PATENT OFFlCE i Claims.

This invention relates to electric signaling systems, and is particularly adapted for use in conjunction with fire alarm telegraph and signal systems, more particularly for use in connection with equipment as contemplated generally by my co-pending application for Signal apparatus, filed June 15, 1936, Serial No. 85,311.

"The broad object of the invention, generally stated, is to provide a system wherein transmitted fire alarm signals are recorded at a central office receiving station in a more reliable, faster and more efficient manner than heretofore.

Signaling systems such as those employed for fire alarm telegraph purposes operate over a normally closed loop circuit, to provide constant electrical supervision of the conductors and all apparatus connected serially therein, in order to give an immediate warning in the event any portion of aforesaid circuit should become opened. Since one of the greatest hazards in maintaining an operative loop circuit is an abnormal opening of the circuit, which may be in the line per se, or in the signaling apparatus, it is desirable to provide a system which can expeditiously transfer an energy source or sources from the'normally closed metallic line to the two separate signaling circuits comprising both sides of the abnormally opened loop and a common return conductor. By this provision, energy is supplied to either side of the line and the common return so that in the event any initiating station is actuated in either side of the line, a signal will be transmitted to the central oiiice receiving station.

All of the systems of the telegraph type in use p today depend solely on a coded signal of periodic impulses. This is disadvantageous, for example, if the signaling contacts should fail to control the circuit, an intelligible signal would never reach the central receiving station. Therefore, .to overcome this condition, the present invention contemplates a system so constituted, that once the initiating station is actuated, it will transmit to headquarters an instantaneous, uncoded signal entirely independent of the transmitter mechanism, though a common initiating means is used to control both the coded and the uncoded signals.

Speed and efiiciency in fire alarm and similar signaling systems are today demanded for public safety. Even though a system is so constituted as to create currents of varying characteristics for the operation of several independent manifestation devices, it is not expedient to operate a In all of the conventional systems now in use which utilize transmitters of the non-interfering succession type, there is a critical range of transmitter shunting resistance which permits sufiicient direct current to flow through the non- 5 interference magnets so that the transmitter armature is retained in its portative position while shunted as described above. Although the transmitter circuit controlling contacts will open and close in their usual manner, the sensitivity of the 3,9

conventional central office equipment is such that it is unable to detect the introductionof the aforesaid shunting resistance serially into the circuit which occurs at eachopening of the transmitter contacts. This invention maintains energy sources .of such characteristics and manifestation devices co-operative therewith, that regardless of the ohmic value in the critical range, of an abnormal shunt across a box, or even across several boxes, headquarters would receive not only a coded signal,but also an instantaneous tell-tale signal,

each of which would positively identify the particular station actuated.

The prior art discloses that in the event of an abnormal open circuit in the loop continuity of a system utilizing a common return, as a ground, the conventional systems employ only a coded signal, using either unidirectional current, or an alternating current, but not both simultaneously.

The present invention under the conditions of an open loop circuit, contemplates not only the utilization of unidirectional current, or an alternating current, for a coded signal, but by superimposition and subsequent segregation of one 35 or more alternating or carrier currents of distinguishable frequency characteristics, there is received at headquarters two coded signals, one formulated in a circuit having unidirectional current and a second formulated ina circuit having alternating current, and a third signal uncoded in character.

Under "varying conditions of the loop circuit, the several diagrams herewith illustrate how par- 45 ticular features of the invention may be employed in various combinations to meet a number of conditions heretofore considered as serious V obstacles.

While manual operation, is possible with this invention for conditioning the loop circuit, to cope with emergency requirements, it is highly -desirable to provide for such circuit manipula tion by automatic means. This becomes a neces-.

sity where a fire alarm headquarters is normally unattended, and constant supervision of the system is not maintained.

The prior art shows that in all fire alarm systems employing transmitters of the successive non-interfering type, if several transmitters in the same loop circuit are operated to initiate alarm signals while that circuit is busy, each transmitter must await an idle condition of the line occurring during the transmitter feeling-in period before its signal can be transmitted over the circuit.

This invention contemplates the transmission of an uncoded identifying signal of a type not requiring an idle condition of the line, thereby substantially eliminating all delay in transmission of individual alarm signals to the central office, irrespective of busy line conditions. In effect, this system will operate exactly as though an individual circuit were provided for each of the transmitters connected to the system, thereby eliminating the necessity of the positive noninterfering succession type of transmitter. By simple modification in a system utilizing transmitters of the interfering type, it may be transformed from an interfering system to an efficient system having non-interfering and instantaneous signaling features.

An object of this invention is to overcome the difficulties hereinbefore set forth and to eliminate other undesirable features inherent in con- Ventional systems. A further object is to provide a system to permit the simultaneous transmission and manifestation of identifying alarm signals from a plurality of signal transmitters serially connected in a single closed loop circuit.

Another object is to provide a system having a plurality of independent manifestation means actuated by separate current sources having frequency characteristics permitting them to be individually controlled by the use of suitable filters. Further objects are the provision of a system having signal transmitters with suitable filters for the selective actuation of manifestation means responsive to individual frequencies; to provide means for superimposition upon existing signal circuits, of distinctive supplementary signals; to provide a system capable of manifesting supplementary signals received from a signal transmitter of the successive non-interfering type, the plain non-interfering type, or of the interfering type, provided such transmitters are equipped with suitable filtering and switching means; to provide a system for superimposing, through electrical coupling means, a current over a circuit to actuate supplementary equipment; to provide means for automatically conditioning an abnormal loop whereby separate currents having distinct characteristics will remain impressed upon both legs of the line; to provide means for impressing signaling waves of carrier frequency upon a normally energized loop circuit, in combination with coupling means and manifestation devices permitting coded and uncoded signals to be simultaneously received; to provide means for transfer of one or more energy sources from one signaling circuit to one or more different signaling circuits under abnormal line conditions.

Other and further objects and advantages of the invention will be hereinafter set forth and the novel features thereof defined by the appended claims.

For a better understanding of the invention, reference may be had to the accompanying drawings, in which:

Fig. 1 is a diagram illustrating the normal loop circuit having instrumentalities for superimposing and manifesting current of a selected frequency.

Figs. 2 and 3 are diagrams showing modifications of Fig. 1 for a conditioned abnormal loop circuit.

Fig. 4 is a diagram showing paths of the unidirectional current.

Figs. 5 and 7 respectively, are diagrammatic showings of a coded, and an uncoded alternating current path.

Fig. 6 is a representation of certain conditions of the loop circuit.

Fig. 8 is a diagram showing means for automatically conditioning and normalizing a loop as represented in Fig. 3.

Fig. 9 is a diagram illustrating means for superimposing and manifesting a multiplicity of currents, in conjunction with means for automatically conditioning and normalizing a loop as represented in Fig. 2.

Referring now to the drawings and especially Figures 1, 2 and 3, A and B are signal transmitting stations, more commonly called, and hereinafter referred to, as boxes. The boxes A and B may be any suitable box operable on a system adapted to utilize a common return conductor, such as a ground, but for purpose of explanation, are boxes particularly adapted for use on the present novel system. The boxes in operation with this system will be hereinafter described in detail.

In Fig. 1, boxes A and B are connected by means of conductors I, 2 and 4, to terminals 5, and 6; said boxes and conductors comprising the outer, or external loop circuit, connected to the central receiving station, or headquarters equipment. A direct current energy source symbolically shown as a transformer primary 31, with a secondary 31', that feeds a rectifier I, is connected in parallel with a storage battery 8, to terminals 9, and II]. In series with the energy sources'I, and 8, and connected on either side thereof, through conductors I I, and I2, to terminals 5, and 6, respectively, are manifestation means I3, and I 4, responsive to unidirectional current impulses. Coupling means herein shown as condensers I5, and IE, are connected respectively from the common terminal 34, to conductors II, and I2, providing a path for currents of carrier frequency, but effectively blocking the flow of direct current.

An alternating current shource is disclosed as a transformer secondary 27', having two terminals, one terminal being connected to the common terminal 34 intermediate two condensers I5, and I6, and the other end of said source connected to one side of a device responsive to alternating current impulses, shown as a selective relay I! and its associated BPFIS. The filter I9 for relay II, has its other terminal connected to a common return 15. Associated with the coil of the relay I1, is shown a band pass filter I9.

general immediately above, is connected across the line through conductors II, and I2, to terminals 5, and E, of the'loop. From the foregoing it will be seen that connected to terminals 5, and 6, are two energy sources of separate'and distinct characteristics. One of the energy sources being direct current, and the second source being an alternating current.

In Figs. 2, and 3, the diagrams are represented as modifications of Fig. l, and set forth the underlying principle of a loop, conditioned to meet an emergency requirement, more particularly, an open in the loop continuity as represented by X in the conductor 2. In these two figures, no means are shown for obtaining the results as diagrammatically expressed in the Figures 2, and 3. However, it is understood that the desired results may be obtained by either manual or automatic switching. l

In all instances wherethe lines Ll, L2, and L3 are shown in part dotted, it is understood to be merely symbolic of a dividing point between the central ofi'ice equipment, and the outer loop circuit. This is done to simplify explanation where it is desirous of showing transposition of a particular phase of one diagram to be used in conjunction with a part or entirety of another diagram.

It is understood by those skilled in the art, that the direct current signals are formulated in the conventional transmitting devices by employing a code wheel to make and break contacts which control the unidirectional current flow in the circuit. This well known aspect, as set forth in the patent to N. H. Suren, No. 1,664,952, and other patents, is utilized in this invention. However, one phase of this invention employs the same contacts to control not only the direct current flow, but also the fiow of an alternating current, as set up by an energy source, such as a transformer having a primary 2! and'a secondary 21, which source may provide any suitable frequency.

Particularly referring to Fig. 2, since the conditioning of the line has taken place, there are 7 now two distinct and separate circuits, each of which is capable of operating on direct current, and having an independent register in each of the circuits. i

For example, if box A is initiated, or pulled, a current will flow from one terminal of rectifier 1, over the conductor 28, through register I3, over the line Ll, through the box, and then to a common return, through a low pass filter 29, (such as a choke coil) and back to the other side of the rectifier.

If box B is pulled, current will fiow from the battery, through a conductor 3!, to terminal Ill, through the register it, out over line L2, through the box B, over a common return, shown as a ground, through the low pass filter 30, and back to battery.

It will thus be seen that each side, or leg of the loop is connected to a separate energy source. Therefore, all boxes initiated on either leg of the former loop, will be suitably connected to its associated register for direct current operation.

To more clearly comprehend the operation of the particular alternating current phase of this novel invention, shown in Fig. 2, let us assume that both of the direct current responsive manifestation means, it, and It, are disconnected at terminals 32, and 33, respectively. If box A is pulled, the code wheel contacts which control the direct current flow, will also operate to control the alternating current flow, thereby formulating a signal which will cause current to flow from the energy source 21, to 21-, over a conductor 35, through the filter 15, over a conductor 36, to terminal 32, over line Ll, through the box A, over a common return, and by means of the selective filter l9, through the relay IT, back to the energy source. The relay l1, will control the local circuit, hereinbefore explained, to actuate the register 23, responsive to each current impulse caused by operation of the code wheel contacts.

If box B is pulled when no other signal is being transmitted, the operation and consequent result will be the same as set forth for box A.

Under normal operation, as shown in Figures 1, and 2, due to the presence of the filters, or condensers l5, and 16, which allow only alternating current to pass therethrough, direct current is prevented from flowing to the alternating current common return to thereby shunt out the transmitters on the line. Likewise, the low pass filters 29, and 30, permit only direct current to pass, and prevent the alternating current from completing itscircuit through the direct current source and its associated parts, to thereby shunt out the transmitter on the line. It will thus be seen that under both the normal and the abnormal conditions of the loop, (Figs. 1 and 2) any box pulled will simultaneously control current of two different characteristics, and record at headquarters two independent coded signals.

A modification of Fig. 2 is shown in Fig. 3, and said modification is particularly adapted to meet service requirements where there is only a single source of direct current energy, as a battery S, a rectifier 1, or an individual motorgenerator set 38. This is a common condition where an existing system uses A and B batteries only, having one set in use while the other set is being charged, or where a common battery is maintained as a source of reserve power to drive a motor-generator set which supplies emergency power for a rectifier unit, it being understood that if the motor-generator set produced direct current, this current would be fed directly tothe line.

The operation of the conditioned loop as disclosed in Fig. 3, is substantially similar in part, to that of Fig. 2. the operation is identical with that of Fig. 2, when box A is pulled, except that since there is no superimposition of alternating current upon the direct current circuit in the central ofilce equipment, no low-pass filter, such as 30, is required.

If box A is pulled, Fig. 3, the operation is identical with that of Fig. 2, when box B is pulled, except that the condenser I6, is not in the circuit.

In Fig. 3, when box B is pulled,

The elimination of the condenser it, permits each side of the conditioned loop to operate as an independent circuit, one side operating from an alternating current source, and the other side operating on a direct current source.

System current paths The embodiments shown in Figures 4, 5, and '7, in each instance, discloses central ofiice apparatus having an energy source. The characteristics of said source in each view, is different from either of the sources shown in the other two diagrams. Connected with each central office energy source and its associated parts are lines L1, L2, and L3, which in turn are connected to, in each showing, a typical transmitter to be employed in part, or in the entirety, with the system as contemplated by this novel invention. These particular diagrams indicate by conventional symbols the path selected by each of the individual currents through the box, in response to its associated central office apparatus adapted for use with each of the distinct currents.

In practice, under various conditions, any one, or more than one, in mixed combinations, of the current paths in the box, may be in service at the same time.

In order to more fully comprehend an objective of the system, it is pointed out that while the invention contemplates superimposing alternating current on a direct current normally energized signaling circuit, the reverse may be equally effective to attain desired results, depending on service requirements.

The invention is so constituted that by the flexible utilization of frequencies in the carrier range, telephonic communication may be efficiently maintained over the normal signaling circuit without interference with any of the manifestation devices at the central receiving station.

Where telephonic communication is to be used on the system, the currents employed for actuation of the central office manifestation devices, may have frequencies as low as 5,000 cycles, but preferably 20,000 cycles, depending on the telephone equipment employed. Any suitable frequencies may be impressed upon the system, up to a maximum frequency which is determined by the physical characteristics of the transmission system, such as resistance, inductance and capacitance per unit length of conductor, and the total length of the signaling circuit involved.

Accordingly, where the system is not used for telephone communication, the maximum. frequency is limited as presented above, but the entire range of audible frequencies is now made available. The minimum frequency will be in the neighborhood of 10 cycles, and limited only by the practical considerations involved in conveniently providing suitable filters capable of distinguishing between the lowest frequency used, and the low frequency alternating current components of the signal impulses originated in the closed circuit by operation of initiating stations. Such low frequency components ordinarily lie within the range of one quarter of a cycle to eight cycles. It is understood from the foregoing that by the use of the expression alternating current, no restrictions other than the above, are to be implied with respect to the frequencies involved. 1

Transmitter Briefly setting forth the devices and instrumentalities in the box, the details of which are more definitely presented in my co-pending application, electro-magnets 40 and 40', are connected in shunt with non-inductive resistors 4| and 4|. The terminals on one end of each electro-magnet and resistor, are connected to the terminals on one end of the second electro-magnet and resistor, actually giving these four terminals a common connection, as at terminal 42. The opposite ends of parts 40, 4|, are connected to a terminal 43. and the parts 4|),4l, are connected to a terminal 44. Each of the terminals 43 and 44 is connected through contact sets 45 and 46, which are actuated by a code wheel sender arm, not shown. These contact sets are connected so as to interrupt, substantially simultaneously, the circuit intermediate terminals 43, 44,

and lines LI, and L2, respectively. Across lines L|, L2, is connected a switch, or box shunt 41, which is closed when the box is in an inoperative condition, to maintain circuit continuity and reduce line resistance. Also across Ll, L2, is placed a high-pass filter 48, the characteristics of which permit the passage therethrough only of alternating current. From one side of the line L2, a switch 54, is serially connected to a selective band-pass filter 49, to a common return line L3. Between the terminal 42, and the common return, there is serially connected a switch 5|, and a band-pass filter l9, heretofore described. Also between the terminal 42, and L3 there is a switch 52, (actuated by the transmitter mechanism, not shown) in series with a low-pass filter 53, said filter having such characteristics as to satisfactorily segregate the direct current from the lowest frequency used in the system.

Transmitter current paths In Fig. 4, when the box shunt 41 is open, and the contact sets 45, 46, are closed, a direct ourrent circuit may be traced from the positive side of the battery over line Ll, through contact set 45, to the terminal 43, where the current is divided, part passing through 40, and part passing through 4|, to terminal 42, again separating to pass through 40, 4|, to terminal 44, contact set 45, over line L2, through the register 4 and to the negative side of the battery.

When an emergency condition of the loop arises, as at X in Fig. 6, the loop circuit is then interrupted. The transmitter mechanism actuates switch 52 and connects terminal 42 to the common return, as a third wire, cable sheath, or ground. The box would then send its signal over either side of the line, depending on where the loop break occurred, through a common return, to a manifestation device at headquarters.

When the box is actuated to transmit a signal, switches 5| and 54, close substantially simultaneously with the opening of the box shunt switch 41.

In Fig. 5 the alternating current central office equipment is identical with that heretofore set forth in reference to Fig. 2, and is connected to both sides of the loop and terminal 34.

The shunts 4|, 4|, are provided because the electro- magnets 40, 40 have an impedance prohibitive to the passage of sumcient alternating current for operation of the system. Due to the presence of the low-pass filter 53, which prevents passage therethrough of alternating current, it will be immaterial whether or not the switch 52 is closed. Since switch 5| is closed when the box is in operation, the relay I1 is energized, preparatory to releasing its armature to control the register circuit when the contact sets 45, 46, are actuated.

In operation, when the code wheel sender actuated contacts close, the alternating current, selected from a plurality of frequencies, (here shown as a single frequency), by filters L9 and IS in this particular circuit, passes from the central oflice equipment over Ll, L2 through the contact sets 45, 46, non-inductive resistors 4|, 4|, unite at terminal 42, passes through 5| and I9, over L3 and back to the central oflice equipment to operate register 23. It will thus be seen that the code wheel sender which controls the direct current over a normal loop circuit, also controls a superimposed current over either or both sides of the line LI, L2, and a common return L3.

The embodiment in Fig. 7 shows the central of the conventional systems.

ofiice apparatus to be a single distinct alternating current source, an annunciator which may be of any suitable type, a selective filter for the annunciator, and two coupling condensers.

The instant the box is initiated to transmit a signal, switch 41 is opened, and switch 54 is closed. A selective high-pass filter 48, across the lines Ll, L2 provides alternating current circuit continuity for other boxes during the time switch 4'! is open. Current flows over the line LI and the high-pass filter 48, and directly from line L2, through the switch 54, selective band-pass filter 49, over the common return to the source 39, annunciator 56 and its associated filter 56', to the coupling condensers back to the lines LI and L2. Itwill be seen that regardless of a break in either side of the loop per se, connected to the box, current will be controlled by the switch .54, to cause immediate actuation of the annunciator 56. 7

From the foregoing statements referring to Figs. 4, 5, and '7, it is manifest that amultiplicity of currents may be superimposed upon and transmitted over the normal metallic loop. When at least three currents are impressed upon this system, each current having distinct and separable characteristics, any current, or combinations of currents, may be controlled to actuate station identifying manifestation means, or a plurality thereof. The coded alternating current controlled by the code wheel sender actuated contact sets is common to all boxes on that particular circuit. The uncoded, or instantaneous signal in one box is distinct and separable from every other box, each box having an individual identifying annunciator located at the central receiving station.

To meet certain service requirements demanding a coded signal, as common in the art, the annunciator and its corresponding instrumentalities may be utilized in conjunction with any The feature of the annunciator in combination with an initiating station for coding signals by interruption of current flow as employed in this novel system'is of vital importance in signaling of the class presented herewith, said annunciator being the maximum in speed operation, giving an instantaneous signal prior to reception of the coded signal, heretofore unknown in this art.

A definite advantage of the speed signaling feature may be shown by employing this phase of the present invention on a system which utilizes transmitters of the interfering or bull-dog type. in this case, no station signals would be lost, due to mutilation by interfering boxes,-as every station actuated would have a distinct identity, instantaneously manifest at headquarters, thereby transforming the old type interfering system into a new speed type of non-interfering system.

By superimposing alternating currents, which includes currents of carrier frequencies, any conventional system, by slight modification, may be equipped to utilize the dual coded feature of this invention to assure reception of signals in case of failure of the source of energy supplying the closed loop, inoperativeness of direct current central office apparatus, or to cope with difiiculties encountered by low resistance box shunts, more fully set forth hereinafter, and numerous other potential hazards. By utilizing the annunciator feature as set forth in this invention, besides being a tell-tale of a station actuated, among other advantages, there is no time delay due to Alternating current sources Although a multi-frequency generator of the single shaft multiple toothed rotor inductive type has been shown, the use of other forms of multifrequency current supply may be desirable under various conditions and is herein contemplated. Such other forms may be individual alternators, electro-magnetic oscillators, electronic oscillators for single or multiple frequencies, or other suitable generating means, depending on conditions and the frequency desired.

Referring to the unit K, Figs. 9, 1'7 and 19 are a relay and selective filter, respectively, said relay controlling the local battery circuit, as herein previously described. Parts M, N and O are annunciators, used each respectively with highpass filters M, N and O. A motor generator set, MG, is shown having means P, R, R and R", for creating a different and distinct energy source for each of the manifestation-filter units and their associated circuits. Four alternating current energy sources are shown which may be means for creating carrier frequencies. The manifestation-filter unit, lllS is commonly responsive to each actuated transmitter on the circuit, while the three remaining manifestationfilter units are each responsive to one of three actuated transmitters on a circuit as boxes 0, D,

and E, in Fig. 6. Any reasonable number of boxes each having an independent annunciator energy source and suitable corresponding apparatus, may be employed in a circuit on this system.

Selective filters Referring particularly to the filters used in this i system, recapitulating, the low-pass filter separates the direct current from the lowest frequency in use on the system, permitting only direct current to pass therethrough.

The high-pass filters have constants such that all currents will pass therethrolugh except direct current. The main purpose of said filters is to provide alternating current circuit continuity for the passage of individual control currents from the multi-frequency generator for the operation of separate manifestation devices at the central office. While band-pass filters are shown to be used for the purposes defined immediately above, this invention also may employ band elimination filters depending on the type of manifestation device utilized in the central ofiice, and the current associated therewith. For example, if the manifestation devices are of the normally energized type, and the filters serially connected when in operation, band elimination filters Will be required in order to secure selective control of a single frequency of the group flowing through the normally closed multi-frequency path.

This invention also contemplates the use of a plurality of sections in the band-pass filters where the frequencies are closely spaced, and it further contemplates the use of amplifier and rectifying detector means in order to secure operation of manifestation devices at the higher frequencies. The above is not shown but may be included as an integral part of the band-pass filters in the central oifice equipment. Although only condensers have been shown as a coupling means for carrier currents, this invention also contemplates coupling inductively to the closed loop circuit which may be accomplished by means of transformers, and in certain cases it is proposed to include the filter means with the coupling devices to form a selective coupling.

Automatic emergency operation rectifier type alternating current relay, depending on the speed, sensitivity and degree of reliability required.

' The, embodiment shown in Fig. 8, represents a transmitter adapted for use in conjunction with this system, said transmitter being connected through lines Ll, L2 and L3, to central ofiice equipment for conditioning and normalizing a loop circuit as disclosed in Fig. 3. In Fig. 8, for simplicity of explanation, manifestation devices and energy sources therefor, are shown for only two distinct currents.

In the drawings, a single transmitting station is shown connected to lines Ll L2 and L3. which are in turn connected to the central ofiice equipment. A transformer having a primary 31, and

a secondary 31, feeds a rectifier l, which charges a battery 3. A variable resistance 82, controls the current flow to the rectifier. The battery impresses direct current energy across the loop, and under normal conditions, as shown in the diagram, a circuit may be traced from the positive side of battery 8, through a milliammeter 51, a variable resistor 58, a main line relay 59, transmitter contact set 45, magnet 40, shunted by 4|, terminal 42, magnet 46', shunted by 4|, contact set 46, line L2, variable resistor 58, contact 6|], armature 60', to the negative side of the battery. The contact set 6|, normally open, permits no current to flow therethrough from the negative side of the battery.

The current flowing over Ll, energizes magnet 59, of main line relay MLR, which closes contact set 63. Current will then flow from the positive side of the local battery 55, over conductor 62, through contact set 63, over conductor 64, through the time delay transfer control relay CR energizing magnet 65, to terminal 66, over conductor 61, to negative battery. Relay CR being energized, attracts its armature to close contact set 68, permitting current to flow from the positive side of local battery 55, over a section of conductor 62, through contact set 68, magnet 69, of time delay transfer relay TR, then to negative battery. The closure of contact set l0, due to the attraction of the complemental armature member of said contact set by the magnet 69, permits an alternating current path to be traced from one side of the line at terminal 32, over conductor ll, contact set l0, conductor H, condenser l5, terminal 34, condenser l6, to terminal 33 on the other side of the normal metallic line.

The purpose of contact set i0, is shown therefore, to connect, (or disconnect) the alternating tory to actuating the register 23, when the trans mitter circuit control contacts open to deenergize the alternating current magnet, and thereby actuate the register.

When the loop is normal and energized by direct current, relays MLR, CR and TR, are all energized. When the transmitters switch 41, is open, and switch 5i, closed, the condition of the three relays mentioned immediately above, is unchanged, while a fourth relay magnet I1, is energized by alternating current to control the register 23, disposed ina local battery circuit.

Each time the loop circuit is opened due to actuation of the circuit controlling contacts in the transmitter, relay MLR is deenergized. The transfer control relay GR, is a time delay relay the characteristics of which cause its contacts to start to open each time MLR is deenergized, yet the time required to actually open its contacts is a period long-er than the longest normal opening of the line, caused .by the transmitter code wheel actuated circuit controlling contacts. Under normal operation of the loop, relays CR and TR remain energized, and at each actuating cycle of contact sets 4546, signals are recorded by registers I4 and 23.

It is also apparent that if the annunciator central ofiice equipment were provided, the trans mitter switch 49 would control a circuit as shown in Fig. '7, to record a third signal.

An abnormal, or emergency situation which permits the loop circuit to be open for an elapse of time longer than the longest normal operating period,-would cause contact set 68, of CR to open, deenergizing the transfer relay TR, causing the opening of contact set l0, and 606ll', and the closure of set 60-60..

The opening of contact set l6 disconnects the alternating current paths between one side of condenser l5, and the terminal 32, connected to the loop, on the Ll side. Opening of set 6060 disconnects negative battery from the L2 side to the line. The negative side of battery 8, is connected to armature 66, which falls back to engage contact 66". A circuit may now be traced from 66", over conductor 12, through variable resistor 13, which permits direct current control to maintain normal operation of the now independent circuit, through a low-pass filter, shown as a choke coil l4, through conductor '12, to the common return L3, which may be a ground, shown dotted by the conventional symbol [5.

. The transmitter mechanism, shown and described in my co-pending application, is such that due to an abnormal opening of the circuit as hereinbefore set forth, the switch ll, will be pivotally operated to engage contact spring ll. Direct current not being able to pass through BPF l9, will pass through LPF 53. A circuit path may then be traced, from one side of the battery, through MA 51, resistance 58, MLR mag net 59, contact set 45, the coil and its shunt 4U-4| respectively, to terminal 42, through a conductor to contact set 17'Tl, LPF 53, over a common return L3, choke M, resistance 13, contact set 6B---5ll, to the opposite side of the battery.

The direct circuit path is now similar to that shown in part of Fig. 3. Recapitulating, the result of the automatic switching, Fig. 8, to condition the loop, has reduced the basic circuit, as shown in Fig. l, to two individual components as disclosed in Fig. 3.

Contact set 6|, remains open since the time delay normalizing relay NR, is deenergized being responsive only to alternating current which must pass through condenser 16, which is prohibitive to passage therethrough of direct current.

The alternating current apparatus normally, is responsive to alternating currents controlled at any point on the loop. Since the abnormal opening in the external loop circuit, and the resultant opening of contact set 10, said alternating current apparatus is only responsive to currents controlled by transmitter contact set it, Fig. 8, on one side of the line L2, and over the common return L3.

The current path may now be traced from one side of the energy source 27, through It, to terminal 33, over L2, contact set 46, resistor ll, switch 5!, BPF 19, L3, to the manifestation device l7, and BPF Hi, to the other side of the energy source.

Each leg of the loop is now conditioned to properly connect any boX actuated on its respective side of the line, to its associated central oflice apparatus.

When the outer loop is repaired by eliminating the abnormal condition thereof, it is necessary to normalize the circuit, that it might operate on the regular metallic loop. Assuming the abnormal loop break to be repaired, and with no box operating on the line, alternating current will flow from one side of transformer secondary 27', to 34, through It, to 33, over L2, through box shunt switch 41 which is now closed, over Ll, through MLR, resistance 58, ammeter 5'5, to terminal 18, part of current going through battery 8 to armature fill, and part passing through rectifler filter RF, MA 51, conductor 79, also to armature til, then through contact set 6ll'til, which is closed, over conductors l2 and at, to NR, energizing same, through condenser it, over conductor l2, BPF l9 and its associated relay winding H, back to the other side of the alternating current transformer 21.

The time delay normalizing relay NR has characteristics such that its contacts start to close as soon as its magnet is energized, yet the time required to actually close the contact set 6 l, is sufficient to prevent undesirable normalizing, caused by any transmitter code wheel actuated controlling contacts. As soon as contact set iii closes, negative battery is fed from terminal 18,

through conductor 8!, contact set 6i, conductor required for its contacts to close upon energization is greater than a time elapse required to complete four cycles of the signal transmitter code wheel; This prevents the normalization of the circuit during the transmitting period of a sending station controlling the direct current side of the circuit. When the contact sets actuate in TR due to energization of 69, the circuit is again restored to normal.

Optional automatic circuit transfer The embodiment disclosed in Fig. 9, represents automatic means forconditioning and normalizing circuits such as shown in Figures 2 and 1, respectively. The circuit in Fig. 9 represents an energized normal loop connected to a single transmitter, with box shunt n open, preparatory to controlling the circuit upon actuation of transmitter contact sets 45-46.

An energy source having a primary 3'! and a secondary 37, feeds alternating current which is controlled by a variable resistor 82, to a rectifier '5, having a filter RF, said rectifier being used to charge battery 8, which in turn energizes the loop for normal direct current operation.

A direct current circuit may be traced from positive battery, through contact set 8484", over conductor 85, variable resistance 58, magnet LR 9S, energizing same, line Ll, through the transmitter to terminal 42, back to L2, through LR 96, variable resistance 58, MA 51, conductor 85. to negative battery. A circuit may also be traced from the terminal of conductor 86, through contact set BS-i3, to conductor 86, which connects negative battery to negative rectifier. Line relays LR and LR and time delay relay TD are normally energized, while transfer relay MT and time delay relay TD are normally deenergized. LR and LR being energized, and contacts 81 and 81 being in series, a circuit may be traced from positive local battery 55, over conductor 90 and 99, through contact set 81, conductor 9!, contact set 81, conductor 9!, magnet 92 of TD, energizing same, back to negative battery. The contact set 94 of TD is normally open when the magnet 92 is energized. The time delay relay TD has characteristics such that its contacts start to open each time the line relays and TD are energized yet the time required to actually open its contacts is longer than the longest normal opening of the line, caused by the transmitter code wheel actuated circuit controlling contacts.

The first opening of the loop by the transmitter deenergizes the line relays and TD 92. When contact set M closes it prepares relay MT to be energized by closure of TD contact 35. The time delay feature of TD prevents contact set 94 from opening during any normal operation on the normal metallic circuit.

Under normal operation, four manifestation devices will be operated, each definitely identifying the transmitting station actuated. The coded alternating current controls relay H, which operates register 23, said register being responsive to every box operating on that circuit. The transmitter, depending on. the characteristics of BPF 49, will actuate one of the annunciator signals. Registers i3 and M are in a local battery circuit, and are individually controlled by main line relay contact sets 88 and BlLrespectively.

An emergency condition which permits the loop circuit to be open for a lapse of time longer than the longest normal operating period, LR st and LR 96 being deenergized and contact sets 83 and 89 closed, current will fiow from positive local battery over conductor 99, contact sets 39'89, conductor 97, to a terminal 98, through TD 93 energizing same, back to negative battery. The closure of TD 95, feeds positive battery from said contacts, through contact set 94, to MT magnet 99 energizing same, back to local battery negative. As long as the abnormal loop condition exists, MT 99 remains energized. The switching of armature 89 from 84" to 84, removes main battery 8, positive, from the LI side of the line and places said positive battery which feeds through a variable resistance l 09 and LPF 29, to a conductor l8! which connects to a common return L3, which may be a ground 15. Switching of armature 83 from 83 to 83 opens the L2 side of the line intermediate nega tive battery and negative rectifier, and places said negative rectifier, which feeds through contact set 83-83, variable resistor I89, LPF 29, to the common return conductor ma. Closure of MT contact set 85, causes positive battery to feed over 90 through contact set 85, conductor 9?, TD 93 to local battery negative thereby locking TD 93, which is quick releasing, against opening thereof due to a possible simultaneous opening of contact sets LB 88 and LR 89' actuatedby transmitter on opposite sides of the abnormal loop.

The emergency abnormal loop conditioning has caused automatic switching from a condition as represented in Fig. 1, to the individual circuit as shown in Fig. 2. In Fig. 9, annunciator manifestation circuits are shown, which may be utilized with boxes A and B of Fig. 2. Each of the conditioned sides of the abnormal loop may now record three signals.

When the loop is restored to normal by repairing the open condition of same, the positive battery and negative rectifier which are connected at terminal I02, the remaining sides of said battery and rectifier being connected to their respective legs of the line, will impress their combined voltages upon the line to energize relays LRLR' and TD. The relay TD, will, after a short lapse of time, permit contact set 94 to open, causing MT magnet 99 to be deenergized, thereby restoring the circuit to normal.

Tracing the circuit which restores the loop to normal operation, after the break in said loop has been repaired, we find that a circuit is now replete whereby the two sources of energy will be added to cause the actuation of the restoring means in the system.

After the loop has been closed by repairing, a circuit may be traced from the terminal I92, through the resistor Hi9, through the contact set B t-84, to positive battery 8, from negative of battery 8 to a terminal which connects through conductor 96 to the L2 side of the line, and more specifically to one side of the milliammeter MA51. From the same terminal I02, we trace a circuit through a resistor I99, through a contact set 8383, over a conductor 86 to RF which is the filter for the rectifier, to the Ll side of the line, and more specifically to the milliammeter indicated as MA51. It will, thus, be seen that the added voltages of the two sources of energy will now be impressed upon the loop conductors LI and L2. Since the loop has been repaired, it is clear that the circuit from the Li side of the line may be traced from the opposite side of the milliammeter MA--'l, through a resistor 58, the winding 98 of LB to terminal 32, through the shunt switch 41, to the L2 side of the line, 32, 96 of LR, resistor 58,

to the opposite side of the MA-51 on the L2 side of the line.

Since this has occurred, both of the magnets 96 and 96 of LB. and LR, respectively, will be energized and attract their respective armatures. The attraction of the armatures which close contact sets 87 and 81 will energize 92 of TD. The energization of the 92 relay will attract the armature of contact set 94, which contact set will open after a period of time which is longer than the longest normal opening in the line due to coded signal transmission. As soon as 94 has opened, the relay 99 of MT will be deenergized, and will result in the armatures of said relay MT falling back to normal. .When the relay MT has been restored to normal, it will be seen that the positive side of the battery 8 is impressed upon the Ll side of the line and the negative side of battery 8 is impressed upon the L2 side of the line. The positive side of the rectifier is impressed upon the Li side of the line and the negative side of said rectifier, through contact sets 83-83, is impressed upon the L2 side of the line. When this condition exists, the circuit will be then restored to normal.

Operation under adverse conditions.

The foregoing disclosure shows that the system contemplated by this invention will automatically facilitate effective conditioning of the circuit to meet emergency requirements generally encountered in practice. This system will also overcome many common difiiculties which are not remedied by any of the conventional systems employed today.

For example, assume two or more alarms are pulled simultaneously, or nearly so, which is not an uncommon occurrence, frequently happening when several boxes situated in a given locality, are pulled to transmit the warning of a single fire. Referring to Fig. 6, assume the circuit is normal, and boxes C and D are pulled, and one box, as box C has an open circuit in a noninterference magnet.

With the conventional transmitters employing a ground system and using non-interfering magnets, there would be a predetermined lapse of time when, after the box shunt is removed, the loop circuit, due to the open coil in box C, would be actually open. Box D, and any other box, as E, pulled during the time interval of the open loop condition, mentioned above, would. switch to ground, and be mechanically locked in as an interfering box. The box is then referred to, by those skilled in the art, as operating bull-dog, and is commonly referred to as an interfering or bull-dog box. With this condition an unintelligible mutilated signal is received at headquarters and all boxes are said to be lost.

The present invention eliminates this undesirable hazard, and under conditions stated above, even though a non-interfering magnet has an open circuit therein, the normal continuity of the loop circuit is maintained, due to the presence of the non-inductive shunt connected across each individual magnet coil, and the magnetic effectiveness of the remaining magnet coil would maintain the transmitter as one possessing noninterfering characteristics.

The protective shunt of the transmitter in this invention positively prevents an open circuit, as specified in the example above. Box D, and all subsequently pulled boxes, would operate non-interfering succession over the regular metallic loop, thereby avoiding the necessity of switching and utilizing an auxiliary com'mon'return circuit, and'preventing the loss of any box.

If in the example given above, both coils are open, thereby destroying the electro magnetic effectiveness of the non-interfering magnet,

boxes of the non-interfering succession grounded type nowemployed, would transmit mutilated signalsand thereby said signals would belost. In the present invention, since box C did not destroy the normal metallic loop circuit, the

second box, D, would seize the line. Box C now having been switched toan interfering position, would also seize the line and start to transmit its particular code signal. The opening of the loop circuit by box Cwould cause box D to release the line and operate in succession until box C completed sendingin its normal signal, whereby the loop circuit would be restored to normal. Box D would then transmit a properly coded signal over the regular metallic circuit.

In all of the conventional systems employing a common return, if an abnormal shunt across a transmitter initiating station is of the value of approximately 20 ohms to 500 ohms, the transmitter, if it operates at all, will operate on what is known as a silent test, and-even though the non-interference magnets remain energized, and the contacts actually operate, no signal capable of actuating a station identifying manifestation device, is received at the central receiving station. Due to the aforesaid shunt, the transmitter mechanism is unable to switch to an auxiliary circuit.

To more clearly express the operation of the box under conditions as presented immediately above, it is known to those skilled in the art that routine testing of the transmitter stations is desirable. One of the routines is known as the silent test. In this test, it is customary to utilize a resistor having a resistance Within the critical range hereinbefore described.

This resistor is used to shunt the transmitter so that it may be actuated to permit its contacts to open and close normally. The operation of the transmitter mechanism may thus be observed under normal conditions without interfering with the normal working of the circuit per se. Due to the small amount of current consumed, the regular register is not operated, however, a sensitive recording manifestation device may be installed at central headquarters for the purpose of observation of electrical reactions, and test supervision.

The embodiment shown in Fig. 6 represents a loop LI and L2 having serially connected therein a multiplicity of boxes as contemplated for particular use in conjunction with this system. L3 is a common return, which may be a ground. In this example, the loop may be open, as represented by X, or may be normal, as shown by the dotted connection at X, across LIL2. Assume that the resistance S, across box F, is 150 ohms, and that the resistances S and S across the line, to a common return, are of any value from 20 ohms to 500 ohms. If box F is pulled, the transmitter will operate on a silent test, but nevertheless will manifest at headquarters, two distinct identifiable signals. If boxes G or H, or any box as C, D or E, are actuated on the unbroken loop, each transmitter pulled will manifest a station identifying signal at headquarters.

From the above it is shown that a new result has been accomplished by this system, namely the reception of a signal from a transmitter located between two faults, such as two low resistancegrounds, and signal reception from a box having an abnormal low resistance shunt.

Accordingly, where return current signaling pathsare of such high resistance that direct current and the lower frequencies cannot be used without resorting to use of excessively high voltages, in such cases there are usually return paths available which would include small amounts of inductive or capacitative coupling, and which constitute excellent signaling paths for frequencies in the upper limits of the useable frequency range.

In the present conventional systems not provided for emergency signaling over an auxiliary path, but employing in said system, transmit ters of the non-interfering succession type, We encounter a serious obstacle due to an open circuit in the non-interference magnet. Where this condition exists in an actuated box, that transmitter operates as an interfering box,'and all stations on the circuit, pulled during the operation of said interfering box, transmit an unintelligible signal, and is lost.

The system provided by this invention may be utilized on a circuit not equipped for transmission over an auxiliary path. Under the conditions expressed immediately above, all boxes subsequently actuated operate normally, and none are lost. This novel accomplishment overcomes one of the gravest handicaps inherent in conventional systems.

While specific details of the system have been herein shown and described, the invention is not confined thereto as changes and alterations may be and may become apparent to those skilled in the art without departing from the spirit thereof as defined by the appended claims.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. Central office mechanisms to provide circuit transfer of two energy sources connected in parallel and having their common terminals electrically tied to the opposite ends of a normally closed loop, means for disconnecting said common terminals and for connecting one side of each of said sources intermediate opposite ends of the normally closed loop and a common return, whereby a double energy source normally impressing current over a single circuit will be divided to urge its components to supply energy to two separate circuits.

2. In a multiconductor utilization system comprising two sides of a line in a closed loop circuit associated with a common return, a plurality of signal initiating stations connected in said loop circuit and each having facilities for completing a connection to the common return, two direct current energy sources connected in parallel and impressed on said loop circuit, means for disconnecting one side of each of said sources from the two sides of the line and connecting said sources to one end of the common return, and manifestation device in each side of the line responsive to initiating stations actuated on its respective side.

3. In an alarm system, the combination of a plurality of signal transmitters, conductors serially connecting the transmitters to form a signaling line, an interconnection between the ends of said line, an emergency return conductor extending from each transmitter, a plurality of energy sources connected between said interconnection and emergency return conductor for impressing currents of different frequencies over both sides of the linethrough the frequency to the current of one of said sources,

and excluding current from the other sources, a pair of separate impulsing means serially connectedinto the line in each transmitter, a connection between the impulsing means of each transmitter and the emergency return conductor of the transmitter, said connection having means therein to pass current of all of said frequencies, a manifestationdevice operable by each current source uponpassage of current therefromthrough the corresponding filter means in a transmitter, and a manifestation device common to all transmitters and operable by current flowing from any of the currentsources through one of said impulsing means.

4. Ina signal system having central office equipment to provide circuit transfer of .two

sourcesof energy, normallyconnected in parallel and urged upona fire alarm loop, a common return conductor, means for automaticallydisconnecting one side of each energy source and conmeeting it to said, common return in response to a prolonged opening of the loop circuit, and means for automatically restoring the two energy sources to normalcy in response to a subsequent prolonged closure of said loop.

5; In a fire alarm signal system having a normally closed loop, a common return, and a plurality of energy sources therefor, circuit transfer means, a timer connected in said loop and responsive to an abnormal openin said loop to cause said timer to actuate said current transfer means to provide two independent signaling circuits-connecting an energy source with one side of the loop and said common return, and a second; energy source with the opposing side of the loop and said'common return.

PAUL P. HOR-NI.

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