US1553337A - Telephone-exchange system - Google Patents

Description

Spt. 15, 1.925. 1,553,337 R. STOKEL Y TELEPHONE EXCHANGE SYSTEM Filed July 26, 1919 3 Sheets-Sheet 1 Owens M II Sept. 15, 1925. 1,553,337

- R. STOKELY v TELEPHONE EXCHANGE SYSTEM Filed July 26, 1919 3 Sheets-Sheet 2 OPE/V5 an I! IWTARYSTEP Mar 1714/ Sept. 15, 1925.

1,553,337 7 R. STDKELY TELEPHONE EXCHANGE SYS'iEM Filed July 26, 1919 :s Sheets-Sheet 5 E30: F5425 wy;

/m/e/1/0/1' Fay Sfd/re/y Patented Sept. 15 1925 UNITED STATES 1,553,337 PATENT OFFICE.

RAY STOKELY, OF FLORAL PARK, NEW YORK, AssIeNoR T0 WESTERN ELECTRIC ooivr- PANY, INCORPORATED, on NEW YoRx, N. Y., A CoRroRArIoN on NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application fi1ed Ju1y'26, 1919. Serial No. 313,521.

To all whom it may concern:

Be it known that I, RAY STOKELY, a citizen of the United States, residing at Floral Park, Long'Island, in the county of Nassau, State of New York, have invented certain new and useful Improvements in Telephone Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates totelephone exchange systems and particularly to toll switching trunks for use with systems involving automatic offices.

Its object is to provide an improved toll switching trunk which requires only a single pair of conductors between the toll operators position and the automatic oflice over which all the setting and supervisory operations are performed, no grounded circuits whatever being employed.

In the system of this invention the toll operator builds up a connection over a two-conductor trunk including automatic switches to the desired line at the distant automatic oflice. In case the line is idle, a signal in the toll operators cord circuit is operated, whereupon she causes the line to be signalled by depressing a ringing key which results in the ringing generator at the connector in the automatic office being connected to the called line. In case the line is busy, the signal in the cord circuit is not operated and the operator, therefore, does not operate her ringing key but takes care of other calls. Then the line becomes idle, the signal is operated and the operator thereupon depresses her ringing key to start the ringing operation. WVhile she maintains the key actuated, the signal in the cord circuit is effaced to indicate that the ringing apparatus at the connector is functioning properly. When the operator releases the key the signal is again operated. When the called party answers the signal is effaced. WVhen he replaces his receiver it again operates whereupon the operator breaks down the connection.

For a more complete understanding of the invention reference should be had to the following description in connection with the accompanying drawings, wherein Figs.- 1,-

2 and 3 placed end to end with Fig. 1 at the left illustrate a system containing one embodiment of the various features of this in-.

vention.

As shown in the drawings, a trunk circuit A Comprising talking Conductors 1 and 5 extends from a toll switchboard to an automatic exchange. At the toll switchboard there is provided a toll cord circuit 13' for establishing connections between the telephone line C and the trunk circuit A. For the purpose of transmitting the selecting impulses over the trunk circuit for controlling the selector switches at the automatic exchange, there is provided at the toll switchboard a dialing cord circuit D which coopcrates with dialing ack 106 associated with the trunk circuit A. Telephone lines such as E terminate at the automaticexchange For the purpose of convenience, only onetoll cord circuit. B, one dialing cord circuit D, one trunk circuit A and one telephone line E are shown in the drawings. It will be understood of course that a plurality of such trunk circuits, cord circuits and telephone lines are provided in practice. The apparatus shown to the left of line 2-2 in Fig. 1 is located at the toll switchboard while that shown to the right of line 2-2 in Fig. 1 and that of Figs. 2 and 3 is located at the automatic exchange.

The toll operator having been advised that connection is desired between the toll line C (which may be connected with the cord circuit B in any desired well known manner) and telephone line E terminating at an automatic exchange, Connection with which must be established by way'of the trunk circuit extending between the toll switchboard and the automatic exchange, inserts plug 110 of the Cord Circuit B into jack 111 of the trunk circuit A. Relays 112 and 113 thereupon operate. The operation of relay 113 actuates busy signal 114: associated with a multiple of the jack 111 in which the trunk circuit A terminates. The operation of relay 113 alsocbridges polarized relay 115 across the talking conductors of trunk circuit A. This polarized relay 115, however, does not operate at this time because the direction of the fiow of current which is fed through the windings of an impulse relay 116 to the talking conductors 4 and 5 is not such as tocause the operation of this relay. Impulse relay 116 however operates over a circuit from battery through the right-hand winding of impulse relay 116, middle left-hand normal contact of re'-' lay 117, lower normal contact of relay 118,

normal contact of relay 119, windings of polarized relay 115, right-hand alternate contact of relay 113, upper normal contact of relay 118, outer left-hand normal contact of relay 117, left-hand winding of impulse relay 116 and the contact 120 to ground. The operationo-f impulse relay 116 causes the energization of slow release relay 121 which prepares a circuit for primary magnet 122 and slow release relay 123.

The operator after inserting the'plug of cord circuit B into the jack of trunkcircuit A may insert the plug of the dialing cord circuit D into the dialing jack 106 thereby causing the operation of relay 124 which at its left-hand contact establishes a holding circuit for'busy signal 114 and at its righthand contact closes the circuit of and causes the energizationof' relay 118. The operation of relay 118 disconnects the jack 111 from the conductors 4 and '5 of the trunk circuit extending to the impulse relay 116 and connects these conductors through the dialing jack 106 with the dialing'cord circuit D, Relay 118 is provided with makebetore-break contacts so that this change does not affect the operated condition of impulse relay 116, which remains energized over a circuit including the contact of the operators impulse sending device 150.

The operator may now actuate the dial 150 to send out a setof impulses representing the thousands digit of the called for line, to cause a series of interruptions in the circuit containing impulse relay 116. At

each interruption of this circuit, impulse relay 116 releases its armatures but relay 121 which is sloW-to-release holds up during these interruptions. 'With the first release of the armature of impulse relay 116, primary magnet 112 and slow release relay 123 energize over a circuit closed-from battery through the windings of primary magnet 122 and slow release relay 123, left-hand alternate contact of slow release relay 121, inner left-hand normal contact of relay 117 and the normal contact of impulse relay 116 to ground. I

The first selector is provided with the usual brushes 132, 133 and 134 which cooperate with a plurality of sets of contacts, to wnich are connected-conductors extending to a second selector, and. also with the usual primary magnet 122, secondary magnet 130 and release magnet 131. These se-' lector switches and the connector switch are preferably of the step-by-step twomovement type in which the primary magnet controls the vertical movement of the brushes, the secondary magnet controls the rotary movement and the release magnet controls the restoration of the brushes tonormal position.

Each energization of primary magnet 122 over the circuit previously traced, causes the one-step vertical movement of the brushes 132, 133 and 134 of this first selector. Upon the first vertical step of the brushes, the primary oil normal contacts 135 and 136 are closed. Marginal relay 137 thereupon operates over a circuit from battery through the winding of marginal rclay 137, P. O.'N. contact 136, alternate contact of slow release relay 123 and the righthand alternate contact of slow release relay 121 to ground. Relay 137 thereupon locks up over a circuit from battery through its winding, 'P. O. N. contact 136, contact of the secondary magnet 130, and the righthand contact of relay 137 to ground.

I hen the last impulse of the first set has been sent,'impulse relay 116 remains ener gized causing the release of primary magnet 122 and slow release relay 123. Upon the closure of the normal contact of slow release relay 123, secondary magnet 130 is operated over a circuit from battery through the winding of secondary magnet 130, left-hand contact of marginal relay 137, normal contact of slow release relay 123 and the right-hand alternate contact of slow release relay 121 to ground. Secondary magnet 130 upon en ergizing opens the locking circuit of marginal relay 137 which thereupon releases its armatures opening the circuit of the secondary magnet130. This secondary magnet 130 controls the hunting movement of the first selector switch. The sleeve terminals of all links extending to busy second selector switches will be grounded so that if the brush 134 engages a grounded sleeve terminal, marginal relav 137, upon the de;- energization of the secondary magnet 130, again energizes over a circuit from battery through the Winding of marginal relay 137, P. O. N. contact 136, contact of the sec ondary magnet 130, right-hand normal contact of relay 117, brush 134 and the grounded sleeve terminal engaged thereby. This ground connection through the brush 134 from the point 138 serves to short-circuit the inding of relay 117. Relay 137 upon energizing closes'the energizing circuit of the secondary magnet 130 which thereupon causes the brushes 132, 133 and 134 to rotate another step. The right-hand contact of relay 137 is closed upon the energization of this relay, connecting ground to the point 138. This ground serves to maintain the relay 117 short-circuited while the brushes are moving from one set of contacts teamother. Marginal relay 187 and secondary magnet 180 continue to energize alternately opening the energizing circuits of each other until the brush 13% engages a nongrounded sleeve terminal whereupon the short circuit is removed from about the winding of relay 117 permitting the energization of this relay over a circuit from battery through the winding of relay 137, P. O. N. contact 136, contact of the secondary magnet 180, winding of relay 117, contact 189 and the right-hand alternate contact of slow release relay 121 to ground. Relay 137 is marginal, and when in series with the winding of relay 117, does not receive sufficient current to permit the closure 01 its contacts. Relay 117 upon being energized opens its normal and closes its alternate contacts. The opening of its outer and middle left-hand normal contacts disconnects impulse relay 116 from the dialing cord circuit D and the closure of the outer and middle lett-hand alternate contacts of relay 117 extends the connection through the first selector to the second selector (shown in Fig. 2). The closure of the right-hand alternate contact of relay 117 causes the energization of a slow-release relay 201 over a circuit from battery through the winding of slow release relay 201, inner right-hand normal contact of relay 202, sleeve terminal and engaging brush 134, right-hand alternate contact of relay 117 and the right-hand alternate contact of slow release relay 121 to ground. Relay 201' causes the energization of signal control relay 203. The energization of this relay 203 opens contacts in the circuits of ringing response relay 204, supervisory relay 280 and reversing or pole-changing relay 205. The energization of relay 208 also connects its left-hand winding through the right-hand windings of repeating coil 206 with the trunk conductors extending to the second selector.

Upon the closure of the outer and middle left-hand alternate contacts of relay 117, impulse relay 207 operates over a circuit from battery through the right-hand winding of impulse relay 207, outer right-hand normal contact of relay 208, outer right-- hand normal contact of relay 209, outer left- 7 hand normal contact of relay 205, brush 133, middle left-hand alternate contact of re lay 117, lower alternate contact of relay 118, contact of the operators dial or sending device 150, upper alternate contact of relay 118, outer left-hand alternate contact of relay 117, brush 182, inner left-hand normal contact of relay 205, inner right-hand normal contact of relay 209, inner right-hand normal contact of relay 208, left-hand winding of impulse relay 207 and contact 210 to ground. Slow release relay 211 thereupon operates over a circuit from battery through the winding of relay 211, alternate contact of impulse relay 207 and the lefthand normal contact of relay .208 to ground. Impulse relay 207 and slow-to-release relay 211 operate before slow release relay 121 releases due to the deenergization of impulse relay 116 following the energization of relay 117, and thereby establish holding circuits for relays 117 and 201. The holding circuit of the former may be traced from battery through the winding of marginal relay 137, P. O. N. contact 186, contact of the secondary magnet 130, winding of relay 117, contact 139, right-hand alternate con-' tact of relay .117, brush 13 1 and the righthand alternate contact of slow release relay 211 to ground. The holding circuit for slow release relay 201 may be traced from battery through the winding of relay 201, inner right-hand normal contact of relay 202 and'the right-hand alternate contact 01": slow release relay 211 to ground.

The operator at the toll switchboard may actuate the sending device 150 to transmit the next; set of impulses which represents the hundreds digit of the number of the called line. Upon the first interruption of the circuit of impulse relay 207, due to the opening of the contact of the sending device 150, primary magnet 215 and slow release relay 216 operate over a circuit from battery through the windings of primary magnet 215 and slow'release relay 216, middle right-hand normal "contactof relay 202, right-hand normal contact of relay 205, left-hand alternate contact of slow release relay 211, normal contact of impulse relay 207 and the lefthand normal contact of relay 208 to ground. Each energization of the primary magnet 215 causes a vertical step of brushes 220, 221, 222 and 223 of the second selector. Upon the first vertical movement of the brushes the primary offnormal contacts 217 and 218 are closed and remain closed until the restoration of the brushes to normal position. The closure of P. O. N. contact 218 causes the energization of marginal relay 224 over a circuit from battery through the winding of contact 224 P. 0. N. contact 218, alternate contact of slow relay 216 and the right-hand alternate contactot' slow release relay 211 to ground. Marginal relay 224C upon being energized completes a locking circuit "for itself from battery through the winding thereof, P. O. N. contact 218, contact of secondary magnet 225, right-hand contact of relay 224 and the normal contact of release magnet 226 to ground. Relays 211 and 216 are slow in releasing so that they do not release their armatures during the short interruptions of their energizing circuits due to the operation of the sending device 150. Impulse re lay 207 and primary magnet 215 however follow these interruptions.

" and the right-handralternate contactof slow release relay 211 to ground. The secondary magnet 225 controls the rotary or hunting movement of the'second selector switch. All

- .busy links extending to the connector switch shown in Fig. 3 will have their associated sleeve terminals at the second selector.

grounded so that when the brush 223 engages a grounded sleeve terminal relay .202 will be short-circuited, due to ground being connected to the point 230 through the grounded sleeve terminal engaging brush 223 and the outer right-hand normal contact of relay 202. As the brush moves from one sleeve terminal to another, the shortcircuit ofwinding of relay 202 is maintained through the normal contact of .release magnet 226 and the right-hand contact of relay 224 to the point 230. The energization of the secondary magnet 225 opens the holding circuit of marginal relay 224 which releases its armature, opening at its left-hand contact the energizing circuit of secondary magnet 225. This secondary magnet therefor releases its armaturesagainestablishing the energizing circuit of marginal relay 224 which if brush 223 is in engagement with a grounded sleeve terminal, attracts its armatures. The secondary magnet continues to cause the one step rotary movement of the brushes 220 to 223 inclusive, until an idle link to a connector switch is engaged by these brushes. The brush 223 therefore will find a non-grounded sleeve terminal and the short-circuitof relay 202 will be removed. Relay 202 therefore immediately operatesover a circuit from battery-through the windingof marginal relay 224, P. O. N. contact 218, contact of secondary magnet 225, winding of relay 202, contact 23 1 and the right-hand alternate contact of slow release'relay 211 to ground. Relay 202 therefore-immediately opens its normaland closes its alternate contacts. The closure. of the outer right-hand alternate contact of relay 202 causes the energization of relay 301 over a circuit from battery through the winding of relay 301, sleeve terminal and engaging brush 223,.outer right-hand alternate contact of relay 202 and the righthandv alternate contact of slow release relay 211 to ground. Uponthe engagementof the brushes 220 and 221 with the terminals of the link circuit extending to the connector switch shown in Fig. 3,-a maintaining circuit for relay 203 is established from battery through the outer left-hand normal contact of relay 302, brush 220, outer lefthand alternate contact of relay 202, inner left-hand alternate contact of relay 203, left-hand winding thereof, middle left-hand alternate contact of relay 203, inner lefthand alternat contact of relay 202, lbrush 221 and the inner left-hand normal contact of relay 302 to ground. The opening of the inner right-hand normal contact of relay 202 causes the deenergization of slow release relay 201 opening the energizing circuit of relay 203. The maintaining circuit just traced for relay 203 is however, estab-- lished before the energizing circuit of relay 203 is opened so that this relay is held energized.

The operator at thetoll switchboard may now actuate the sending device 150to transmit a set of impulses representing the tens digits of the number 01 the called line and then another set of impulses representing the units digit of the number of the called.

line. Upon the first interruption of the circuit of impulse relay 207 at the contact of the sending device 150, impulseirelay 207 (releases causing the energization of primary magnet 303 and slow release relay 304 overa circuit from battery, through the windings of primary magnet 303 and slowarelease relay 304, P. O. N. contact 305, brush 222 of the second selector, middle right-hand alt-ernatecontact'of relay 202, right-hand normal contact of relay 205, left-hand alternate contact of slow release relay 211, normal contact of impulse relay 207 and the lefthand normal contact of relay 208 to ground. Upon the energization of primary magnet 303, brushes306, 307 and 308 of the connector switch are moved. one step vertically. Upon the first vertical step of the switch, the primary oil-normal contact 305 is opened and primary oil-normal contacts 309 and 310 are closed.

The energizing circuit for primary magnet 303 and the slow releaserelay 304 then extends through the alternate contact of slow release relay 304 and P. O. N. con

tact 310, rather than throughthe P. O. N.

contact 305. Relay 304 is slow in releasing so that it does not release its armature during the short interruptions which exist during the transmission of the tens .im pulses.

Following thetransmission of the last impulse of the tens series, impulse relay 207 remains energized and primary magnet 303 and slow release relay 304 release. The opening of the alternate contactof slow release relay 304 prevents the reestablishment of the energizing circuit (of primary magnet 303 and the slow release relay 304 until the connector switch has been restored to normal position. 7

Upon the first interruption during the transmission of the units series of impulses by the sending device 150, impulse relay 207 releases its armature causing the energization of secondary magnet 315 and slow release relay 316 over a circuit from battery through the winding of secondary magnet 315, left-hand normal contact of slow release relay 317, winding of relay 316, outer righthand normal contact of relay 302, normal contact 01 slow release relay 304, 1 .0. N. contact 310, brush 222 of the second selector,

. middle right-hand alternate contact of relay 202, right-hand normal contact of relay 205, left-hand alternate contact of slon release relay 211, normal contact of impulse relay 207 and the left-hand normal contact of relay 208 to ground. Secondary magnet 315, upon being energized, causes the brushes 306, 307 and 308 of the connector to be rotated one step. Upon the energization of slow release relay 316, the left-hand alternate contact thereof is connected in parallel with the left-hand normal contact of relay 317 in the energizing circuit of secondary magnet 315 and relay 316. The brushes of the connector switch are rotated in responseto each units impulse until brush 308 engages the sleeve contact of the selected line. After the transmission of the last units impulse, impulse relay 207 remains energized, opening the energizing circuit of the secondary magnet 315 and relay 316. Relay 316 is slow in releasing so that it holds up for a short interval. Immediately afterthe units impulses are sent, the toll operator disconnects the dialing cord D from dialing jack 106, whereupon relays 124 and 118 release, disconnecting the trunk conductors 4 and 5 from the dialing jack and con necting these conductors with the jack 111.

If the selected line is busy the sleeve terminal is grounded so that relay 317 will be energized over a circuit extending from battery through the winding of relay 317, righthand alternate contact of re1ay'316, brush 308 and the grounded terminal engaged by the brush. Upon the energization of relay 317, a locking circuit is established therefor from battery through the winding and the right-hand alternate contact of relay 317, normal contact of relay 316, brush 308 to ground through the engaged terminal. The closure of the lefthand alternate contact of relay 317 connects a busy tone with the trunk conductors extending to the toll switchboard which will indicate to the operator, whose telephone set may be connected in circuit through contacts of the listening key, that the selected line is busy.

If the selected busy line is held until it becomes idle, the removal of ground from the test terminal of this line causes the release of rslay 31'?- Upon the release the eof relay 302 is energized over a circuit from battery through cut-off relay 320, sleeve terminal and engaging brush 308, normal contact of relay 316, right hand normal contact of relay 317, left-hand Winding of relay 302, and the alternate contact of relay 301 to ground. Upon the energization of relay 302, a locking circuit is established therefor from battery through the right-hand winding of relay 302, inner right-hand alternate contact thereof and the alternate contact of relay 301 to ground. The closure of the middle right-hand contact of relay 302 connects ground through brush 308, to the-test terminalof the line E so as to render this line busy.

The opening of the left-hand normal con-' tacts of relay 302 causes the deenergization of relay 203. This relay 203 upon the closure of its right-hand contact causes the energization of pole-changing relay 205 over a circuit from battery through the winding of this relay 205, right-hand contact of re lay 203, inner right-hand alternate contact of relay 202, and the right-hand alternate contact of slow release relay 211 to ground. The energization of relay 205 reverses the battery in circuit including the talking conductors 4 and 5 extending to the toll switchboard, thereby'causing the operation of polarized relay 115 bridged across the talking conductors at the toll switchboard. Relay 115 in operating causes the energization of relay 140 which in turn causes the energization of relay 119. Relay 119 thereupon locks up over a circuit from battery through the winding of relay 119, inner left-hand contact thereof, another normal contact of relay 141 to ground. The opening of the normal contact of relay 119 opens the bridge including the polarized relay 115 thereby disconnecting the polarized relay from the talking conductors of the trunk circuit, and the closure of the inner right-hand alternate contact of relay 119 short circuits condenser 142. The closure of the outer left-hand contact of relay 119 insures that the busy signal 114 will be operated as long as relay 119 is energized regardless of the condition of relay 113. The short circuiting of the condenser 142 permits the energization of supervisory relay 143 bridged across the talking conductors of the cord circuit B. An annunciator, shown as a lamp 144 is thereupon lighted to furnish a ringing sig nal to the operator at the toll switchboard.

Upon observing the lighted condition of the lamp 144, the operator may actuateringing key R to connect a source of ringing current with the trunk circuit for causing the energization of ringing response relay 204. Upon the: energization of ringing re sponserelay 204, relay 209 operates to dis-. connect the impulse relay 207 from the talking conductors and to establish a temporary holding circuit for slow release relay 211 which may be traced from battery through the winding of relay 211 and the left-hand contact of relay 209 to ground. The closure of the left-hand contact of relay 209' also causes the energization of ringing relay'330 over a circuit from battery through i the winding of relay 330,'outer right-hand alternate. contact of relay 302, normalcontact of relay 804, P. 0. N1 contact 310, contact and engaging brush 222 of thesecond selector switch, middle right-hand alternate contact of relay 202, and the left-hand contact of relay 209 to ground. The energization of relay 330 connects a source of ringing current to the connected telephone line E to operatethe usual call bell'at the station on this line. \Vhile the ringing key 'R is actuated, supervisoryrelay 143 is' deencrgi'zed' and' the lamp 144 is extinguished; The restoration of the ringing k y R to normalposition causes the deenergization" of ringing response relay 204 which, in releasin'g,deenerg'izes relay 209. The opening of the left-hand contacts of relay 209 causes the 'deenergization of ringing relay 330 which disconnects ringing current from the calledline. The closure of the right-hand contacts of relay 209 connects impulserelay 207 to the talking conductors of the trunk circuit energizing the impulserelay 207 and supervisory relay 143. The supervisory lamp 144 is thereupon lighted.

The subscriber at the station on telephone "line E; in responding to the operation of the call bell thereat removes the receiver from the switchhook thereby causing the energization'of supervisory relay 230 over a circuit from battery through the winding of supervisory relay 230', middle left-hand normal contact of relay 203, inner left-hand contact of relay 202, brush-I221, inner lefthand alternate contact of relay 302, righthand normal Contact of ringing relay 330, brush 307, out over one side of the line through substationapparatus and back over the other side of the line throughthe brush 306, left-hand normalcontafct or ringing relay 330,0uter left-hand alternate contact of relay 802, brush 220,- outer left-hand contact of relay 202, and the innerleft-hand normal contact of relay 203 to'ground'. The supervisory relay 230 in operating causes the energiz'ation'of relay'208 which in open ing its rig hthand contacts disconnects the impulse relay 207 n and battery from the talking conductors ofthe trunk circuit extending to the toll switchboard. Supervisory relay 1'48 thereby deenergizes extinguishing supervisory lamp 144. The opening ot the leitt -hand' ndrmal contact of relay 208 opens, the energizing circuit of slow release relay 211 but before thi's' rela y releases its armature thei energizing circuit therefor is rest'ablished throngh the' alternate contact of relay 208, thereby holding this relay211 energized. A conversational circuit is now established from the station of the toll line Gthrough the toll cord circuit B and the trunk circuit A to the station on telephone line E.

At the conclusion of the conversation the subscriber at the station on the toll line C gives a disconnect signal by operating the generator thereat causing the energization of relay 145 which locks up lighting supervisory lamp 146. The lightingof this lamp serves as a disconnect signal from the toll line 'C. The restoration of the receiver to the switchhook at the station on telephone line E causes the deenergization of supervisory relay 230 whereupon relay 208 is deenergized and releases its armatures. The release or the armatures of relay 208 connects battery and impulse relay 207 with the talking'conductors of the trunk circuit extending to the toll switchboard. The impulse relay 207 and the supervisory relay 143 thereupon operate, The operation of impulse relay 207' reestablishes the circuit of slow release relay 211. This relay 211 be ing slow to release, does not release its armatures during the short interval between the opening of, the alternate. contact of relay 208 and the closureor the alternate contact of impulse relay 207. The energization of supervisory relay 143 causes the lighting of the supervisory lamp 144 which serves as a disconnect signal from telephone line E to the operator at the toll'board,

Upon observing the lighted condition of the supervisory lamps 144 and 146, the operator may withdraw the plug 110 from the jack 111 whereupon the apparatus of the operators cord circuit is" restored to normal condition; The withdrawal of the plug 110 fromthe jack 111 also causes the deenergization'ot relay 113 which in closing its normal contact bridges relay 141 across the. talking conductorsof the trunk circuit, This relay 141 is thereupon energized over a circuit from battery through the right-hand winding of impulse relay 207,.outer right-hand contact ofrelay 208, outer right-hand contact of relay 209, inner left-hand alternatecontact of relay 205, brush'132, outer left-hand alter nate contact of relay 117, upper normal contact of relay 118,v normal contact ofrelay 113, winding of relay 141, outer right-hand alternate contact of relay 119, lower normal contact of relay 118, middle left-hand alternate c'ontact of relay'117, brush 138, outer left-hand alternate contact of relay 205, inner right-hand contacts of relays 209 and 208, left-hand winding of impulse relay 207 andcontact, 210 to ground. The energization of relay 141 opens the locking circuit of relay 119 which thereupon releases its armaturedisconnecting relay 141 from bridged relation with the talking conductors ofthe trunk circuit A. This relay 141 is thereby deenergized. The energizing circuit for impulse relay 207 is also thereby opened and causes impulse relay 207 to release its armatures. Slow release relay 211 thereupon releases its armatures, and the opening of the right-hand alternate contact thereof causes the release of relays 202 and 117 which re lease their armatures.

The closure of the inner left-hand normal contact of relay 117 causes the energization of release magnet 131 over a circuit from battery through the right-hand winding of release magnet 131, P. O. N. contact 135, normal contact of slow release relay 121,

- inner left-hand normal contact of relay 117,

and the normal contact of impulse relay 116 to ground. The energization of release magnet 131 restores the brushes 132, 133 and 134 of the first selector switch to normal position thereby opening the P. O. N. contacts 135 and 136. The opening of contact 135 causes the deenergization of release magnet 121. The first selector switch and associated apparatus are, therefore, restored to normal condition.

The opening of the right-hand alternate contact of slow release relay 211, due to the release thereof upon the deenergization of impulse relay 207, causes the deenergization of relay 301. Relay 301 in releasing causes the energization of release magnet 325 over a circuit from battery through the Winding of release magnet 325, P. O. N. contact 309 and the normal contact of relay 301 to ground, The energization of release mag net 325 restores the brushes 306, 307 and 308 of the connector switch to normal position. The restoration of the brushes to normal position opens the P. O. N. contacts 309 and 310 and closes P. O. N. contact 305. The apparatus associated with the connector switch is thereby restored to normal condition.

The closure of the normal contact of slow release relay 211 causes the energization of release magnet 226 over a circuit from battery through the winding of release magnet 226, P. O. N. contact 217 and the normal contact of slow release relay 211 to ground. The energization of this release magnet 226 restores brushes 220, 221, 222 and 223 of the second selector switch to normal position. The restoration of these brushes to normal position opens P. O. N. contacts 217 and 218 opening the energizing circuit of release magnet 226. The second selector switch and associated apparatus are therefore restored to normal.

If the toll operator after the party at the static-n on the telephone line E has responded by removing the receiver from the switchhook should desire to change the cord circuit connected with the iack 111 of the trunk circuit A, this may be done without affecting the established connection through the selector switches and the connector switch. The reason for this is that while the receiver at the station on telephone line E is off the switchhook, that is, when the telephone line E is closed at the switchh ook contact, supervisory relay 230. is energized and due tothe resulting energization of re lay 208 battery is disconnected from the two-conductor trunk circuit extendlng to the toll switchboard. Therefore, when relay 113 deenergizes when the plug 110 is disconnected from-the jack 111, the bridging of relay 1 11 across the conductors of the trunk circuit has no effect at all. for there is no source of current for energizing the relay 14:1. Busy signal 114, however, re mains operated due to the closure of the outer left-hand contact of relay 119 which is locked up through the contact of relay 1411. The insertion of the plug oranother cord circuit into the jack 111 merely causes the energization of sleeve relay 113, without affecting the condition of any other apparatus, and removes relay 141 from bridged relation with the conductors of the trunk circuit A.

What is claimed is:

1. In a telephone exchange system, in combination a trunk circuit comprising a pair of talking conductors extending from a first to a second ofiice, a cord circuit at the first office, a supervisory relay therein, a circuit for said relay including said trunk circuit, a telephone line terminating at the second ofiice, means there at for connecting the trunk circuit with the telephone line, a signal control relay at the first ofiice con nected with the talking conductors and controlled by the telephone line, and means rendered effective by the operation of the signal control relay for closing a break in said supervisory relay circuit and for disconnecting said signal, control relay from the talking conductors of the cord circuit during conversation.

2. In a telephone exchange system, in combination, a trunk circuit comprising a pair of talking conductors extending from a first to a second ofiice, a telephone line terminating at the second oifice, means thereat for connecting the trunk circuit with the telephone line, a link circuit at the first office connected with the trunk circuit, a signaling device in the link circuit, a relay at the first oflice connected with the talking conductors and responsive to the idle condition of the selected line for causing the operation of the signaling device, and a relay energized upon the response of the signal control relay to disconnect the sig nal control relay from the talking conduc- I pair of talking conductors extending from a first to a. second office, a telephone line terminating at the second ofiice, means thereat for connecting the trunk circuit with the telephone line, a link circuit at the first office connected with the trunk circuit, a signaling device in the link circuit, a signal control relay at the first ofiice bridged across the talking conductors and responsive to the connection of the trunk circuit with the telephone line, and a relay energizedupon the response of the signal control relay for disconnecting the signal control rel-ayfrom the talking conductors and for causing the operation of the signaling device.

,4. In) a telephone exchange system, in combination, a trunk circuit comprising a pair of talking conductors extending from a first to a second office, one o-f the talking conductors being normally open, a telephone line terminating at the second ofiice, means .the'reat for connecting the trunk circuit with the telephone line, a link circuit at the first otfice connected with the trunk circuit, a signal control relay at the first ofiice bridged across the talking conductors and responsive to the connection of the trunk circuit with the telephone line, a second relay energized upon the response of the signal control relay for closing the normally open talking conductor, and a signaling device in the link circuit operating in response to the closure of the talking conductor.

5. In a telephone exchange system, in combination,a trunk circuit comprising a pair of talking conductorsextending from a first to a second 0ffice, one of the talking conductors being normally open, a telephone line terminating at the second ofiice, means thereat for connecting the trunk circuit with the telephone line, a link circuit at the first ofiice connected with the trunk circuit, a signal control relay at the first office bridged across the talking conductors and responsive to the connection of the trunk circuitwith the telephone line, a second relay energized upon the response of the signal control relay for closing the normally open talking conductor and for opening the bridge including the signal control relay, a locking circuit for the second relay established upon the energization thereof for removing the second relay from control of the signal control relay, and a signaling device in the link circuit operating in response to the closure of the talking conductor.

6. In a telephone exchange system, in combination, a trunk circuit comprising, a pair of talking conductors extending from a first to a second office, a link circuit at the first ofiice connected with the trunk circuit, a polarized relay at the first oifice bridged acrossthe talking conductors, a relay at the second cffice responsive to the idle condition 01 the telephone line for reversing current over the talking conductors to operate the polarized relay, a signaling device in the link circuit controlled by the polarized re.- lay, and a second relay energized by the operation of the polarized relay for opening the bridge including the polarized relay.

7. In a telephone exchange system, in

combination, a trunk circuit"comprising a pair of talking conductors extending from a first to a second office, a telephone line terminating at the second ofiice, means including a selector switch for establishing a connection between the trunk circuit and the telephone line, a stepping magnet for the selector switch, an impulse relay at the second oifice connected with the talking conductors and responsive to impulsestransmitted over the talking conductors from the first oifice for controlling the stepping magnet, a link circuit at the first ofiice connected with the trunk circuit, a polarized relay at the first ofiice connected in bridge with the talking conductors and responsive to a reversal of current over the talking conductors when the selector switch finds the telephone line idle, a signaling device in the link circuit controlled by the polarized rela and a second relay operating upon the response of the polarized relay to open th bridge including the polarized relay.

8 In a telephone exchange system, in combination, a trunk circuit comprising a pair of talking conductors extending from a first to a second ofiice, a telephone line at the second oifice, means including a selector switch for connecting the trunk circuit with the telephone line, a stepping magnet for the selector switch, an impulse relay at the second oifice connected with the talking conductors and responsiv to impulses transmitted thereover from the first ofiice for controlling the stepping magnet, a polarized relay at the first ofiice, a link circuit thereat, means responsive to the connection of the link circuit with the trunk circuit for bridging the polarized relay across the talkin response to the idle condition or" the telephone line to reverse the current over the talking conductors to operate the polarized relay, a signaling device in the link circuit controlled by the polarized relay, and a second relay energized by the operation of the polarized relay for opening the bridge including the polarized relay.

9. In a telephon exchange system, in

mg conductors, a reversing relay operating combination, a trunk circuit comprising a contact, a link circuit at the first office con- I nected with the trunk circuit, a telephone line terminating at the second otfice, means thereat for connecting the trunk circuit with the telephone line, a relay at the first office connected with the talking conductors and responsive to the connection of the trunk circuit with the telephone line for closing the open contact in the talking conductor, and a signaling de ice in the link circuit operating in response to the ole sure of the normally open contact.

10. In a telephone exchange system, in combination, a trunk circuit extending from a first to a second ofiice, a signal control relay at the first office, a link circuit thereat, means responsive to the connection of the link circuit tothe trunk circuit for connecting the signal control relay in operative relation with the trunk circuit, a telephone line terminating at the second ofiice, means thereat responsive to the idle condition of the telephone line for causing the operation of the signal control relay, and means rendered effective upon the operation of the signal control relay for interrupting the operative association thereof with the trunk circuit.

11. In a telephone exchange system, in combination, a trunk circuit comprising a pair of talking conductors extending from a first to a second office, a link circuit at the first otfice connected with the trunk circuit, a condenser at the first ofiice connected in one of the talking conductors, a polarized relay at the first oflice connected in bridge to the talking conductors, a telephone line terminating at the second oflice, means thereat responsive to the connection of the trunk circuit with the telephone line for causing the operation of the polarized relay, and a relay energized by the operation of the polarized relay for removing the condenser from the talking conductor and for opening the bridge including the polarized relay.

12. In a telephone exchange system, in combination, a trunk circuit comprising a pair of talking conductors extending from a first to a second oifice, a link circuit at the first ofiice connected with the trunk circuit, a telephone line terminating at the second ofiice, means thereat including a selector switch for connecting the trunk circuit with the telephone line, a stepping magnet for the selector switch, an impulse relay connected with the talking conductors and responsive to current impulses transmitted over the talking conductors from the first office for controlling the stepping magnet, and a relay responsive to the closure of the connected telephone line for disconnecting the impulse relay from the talking conductors.

13. Ina telephone exchange system, in combination, a trunk circuit extending from a first to a second oflice, a telephone line t rmin ting at each office, means at t e fir olfice for connecting the telephone line terminating thereat with the trunk circuit, a signal control relay initially energized upon an extension of a connection toward the telephone line terminating at the second olfice, means for maintaining the signal control relay energized upon a further extension of the connection toward the line terminating at the second ofiice, and means responsive to the idle condition of the telephone line terminating at the second office for causing the deenergization of the signal control relay.

14. In a telephone exchange system, in combination, a trunk circuit extending from a first to asecond oflice, means including a selector switch and a connector switch for connecting the trunk circuit with the telephone line, a link circuit at the first office connected with the trunk circuit, a signal control relay associated with the trunk circuit and initially energized by the seizure of the selector switch, means responsive to the seizure of the connector switch by the selector switch for establishing a maintaining circuit for the signal control relay, means responsive to the idle condition of the telephone line when connected to by the connector switch for deenergizing the signal control relay, and a signal device in the link circuit responsive to the deenergization of the signal control relay.

15'. In a telephone exchange system, in combination, a trunk circuit extending from a first to a second office, a link" circuit at the first otfice connected with the trunk circuit, a telephone line terminating at the second oflice, means thereat including selector and connector switches controlled over the trunk circuit for establishing connections between the trunk circuit and the telephone line, a signal control relay associated with the trunk circuit and having a plurality of windings, an energizing circuit including one of the windings established in response to the seizure of the selector switch by the trunk circuit, means responsive to the seizure of the connector switch by the selector switch for opening the energizing circuit and establishing a maintaining circuit through a second winding of the signalcontrol relay, means responsive to the seizure of the telephone line by the connector switch for opening the maintaining circuit of the signal control relay, and a signaling devlce in the link circuit controlled by the signal control relay.

16.111 a telephone exchange system, 1n combination, a trunk circuit comprising a pair of talking conductors extending trom a first to a. second ofiice, a link circult at the first oflice connected with the trunk circuit, a telephone line terminating at the selector switch, an impulse relay connected with the talking conductors and responsive to impulses transmitted thereover from the first office for controlling the motor triagnet, a. release control relay at the first otlice bridged across the talking conductors by the disconnection of the link circuit from the trunk circuit, and a release magnet for the selector switch controlled by the bridged release control relay.

17. In a telephone exchange system, in combination, a trunk circuit comprising a pair of talking conductors extending from a first to a second otlice, a link circuit at the first otli ce connected with the trunk circuit, a telephone line terminating at the second office, means thereat including a selector switch for connecting the trunk circuit with the telephone line, a motor magnet for the selector switch, an impulse relay connected with the talking conductors and responsive to impulses transmitted thereover from the first office for controlling the motor magnet, a signal control relay at the first ofiice responsive to the connection of the trunk circuit with the telephone line, a release control relay, a relay responsive to the disconnection of the link circuit from the trunk circuit and co-operating with the signal control relay to bridge the release control relay across the talking conductors, and a release magnet for the selector switch controlled by the release control relay.

18. In a telephone exchange system, the combination with a calling line, a cord circuit, a two conductor trunk, an automatic switch wherein said trunk terminates, other automatic switches, a sender for said cord circuit for controlling said switches to build up a connection to the called line, a signal in said cord circuit, a relay for operating the same, means controlled by the idle condition of the called line for operating said relay over a metallic circuit including said trunk conductors in series, a ringing current generator, a ringing control relay at the distant end of the trunk, and a control circuit for energizing said relay to cause said generator to be connected to the called line, said circuit including the trunk conductors in series, and a key in said cord circuit, adapted to close said control circuit.

19. In a telephone exchange system, the combination with a calling line, a cord cir cuit, a two conductor trunk, an automatic switch wherein said trunk terminates, other automatic switches, a sender for said cord circuit for controlling said switches to build up a connection to the called line, a signal in said cord circuit, means controlled by the idle condition of the called line for operating said relay over a metallic circuit including said trunk conductors in series, means for automatically holding the connection if the line is busy and for delaying the operation of said signal until the line becomes idle, a ringing current generator, a ringing control relay at the distant end of the trunk, and a control circuit for energizing said relay to cause said generator'to be connected to the called line, said circuit including the trunk conductors in series, and a key in said cord circuit adapted to close said control circuit.

20. In a telephone exchange system, the

combination with a calling line, a cord circuit, a trunk, an automatic switch wherein said trunk terminates, other automatic switches, a sender for said cord circuit for controlling said switches to build up a con nection to the called line, an annunciator in said cord circuit, means controlled by the idle condition of the called line for operating said annuciator, and means controlled by the response of the called party for rendering said annuciator inert.

21. In a telephone exchange system, the combination with a calling line, a cord circuit, a trunk, an automatic switch wherein said trunk terminates, other automatic switches, a sender for said cord circuit for controlling said switches to build up a connection to the called line, an annunciator in said cord circuit, means controlled by the idle condition of the called line for operating said 'annunciator, means controlled by the response of the called party for rendering said annunciator inert, and means controlled by the replacement of the receiver by the called party for again operating said annunciator.

22. In a telephone exchange system, the combination with a calling line, a cord circuit, a two conductor trunk, an automatic switch wherein said trunk terminates. other automatic switches, a sender for said cord circuit for controlling said switches to build up a connection to the called line, a supervisory lamp in said cord circuit, a relay controlling the same, means controlled by the idle condition of the called line for operating said relay over a metallic circuit including said trunk conductors in series, means for automatically holding the connection and delaying the lighting of said lamp until the line becomes idle, a ringing current generator at the office wherein the called .line terminates, a ringing control relay thereat, a control circuit for energizing said relay to cause said generator to be connected to the called line, said circuit including the trunk conductors in series, a key in the cord circuit adapted to close said control circuit, and means for rendering said lamp inert upon the response of the called party and for operating the same upon the replacement of the receiver by the called p y 23. In a telephone exchange system, the combination with a calling line, a cord circuit, a two conductor trunk, an automatic Lil switch wherein said trunk terminates, other automatic Switches, a sender for said cord circuit for controlling said switches to build up a connection to the called line, a lamp in said cord circuit, a relay controlling the same, means controlled by the idle condition of the called line for operating said relay over a metallic circuit including said trunk conductors in series, means for automatically holding the connection and de laying the lighting of said lamp until the line becomes idle, a ringing current generator at the oflice wherein the called line terminates, a ringing control-relay thereat, a control circuit for energizing said relay to cause said generator to be connected to the called line, said circuit including the trunk conductors in series, a key in the cord circuit adapted when actuated to close said control circuit, means for rendering said lamp inert while said key is actuated and for operating the same when released, said means being located at the oflice wherein the called line terminates, and means for rendering said lamp inert upon the response of the called party and for operating same upon the replacement of the receiver by the called party.

24:. In a telephone exchange system, a cord circuit, a two-conductor trunk, an automatic switch wherein said trunk terminates, other automatic switches, a called line, means including a sender for said cord circuit for controlling said switches to build up a connection to the called line, a signal in said cord circuit, a relay for operating the same, a polarized relay in a bridge of said cord circuit adapted upon the called line becoming idle to close a break in the circuit of said relay to operate said signal, said circuit including said trunk conductors in series, and means for interrupting said circuit upon the response of the called line to render said signal inert and for again closing the same upon the hanging up of the receiver by the called line to again operate said signal.

25. In a telephone exchange system, a cord circuit, a twoconductor trunk, an automatic switch wherein said trunk terminates, other automatic switches, a called line, means including a sender for said cord circuit for controlling said switches to build up a connection to the called line, a signal in said cord circuit, a relay for operating the same, a polarized relay in a bridge of said cord circuit adapted upon the called line becoming idle to close a break in the circuit of said relay to operate said signal, said circuit including said trunk conductors in series, and means for opening said bridge upon the operation of said relay to remove the same from the talking circuit.

26. In a telephone exchange system, an operators cord circuit, a two-conductor trunk, an automatic switch wherein said trunk terminates, other automatic switches, a called line, means including a sender -for said cord circuit for setting said switches in sequence to build up a connection to the called line, switch releasing means individual to each switch of the train, means responsive to the removal of the cord from the trunk jack before the called line responds for operating each switch releasing means to release all the switches simultaneously, means controlled by the response of the called line for transferring the switchre leasing means from the absolute control of the operator to the combined control of the operator and the called line so that either the operator or the called line may disconnect without releasing the switches.

27. In a telephone exchange system, an operators cord circuit, a trunk circuit, an automatic switch wherein said trunk terminates, other automatic switches, a called line, means including a sender for said cord circuit for setting said switches in sequence to build up a connection to the called line, switch releasing means individual to each switch of the train, means actuated when the cord is removed from the trunk before the called line responds for operating each switch releasing means thereby simultaneously releasing all the switches, means controlled by the response of the called line for removing each switch releasing means from the absolute control of the operator and for subjecting them to the combined control of the operator and the called line so that the operator may change cords without releasing the switches.

28. In a telephone exchange system, an operators cord circuit, a trunk circuit, an automatic switch wherein said trunk terminates, other automatic switches, a called line, means including a sender for said cord circuit for setting said switches in sequence to build up a connection to the called line, means controlled by the operator for signaling the called line, switch releasing means individual to each switch of the train, means actuated when the cord is removed from the trunk before the called line responds for operating each switch releasing means whereby all the switches are simul taneously released, means controlled by the response of the called line for removing each switch releasing means from the absolute control of the operator and for subjecting them to the combined control. of the operator and the called line so that both the op erator and the called line must disconnect in order to release the switches.

29. In a telephone exchange system, an operators position, a trunk circuit, automatic switches accessible thereto, a called line, means controlled by the operator for setting said switches in sequence to build up a connection to the called line, switch releasing means individual to each switch of the train, means controlled by the operator for operating each switch releasing means whereby all the switches are simultaneously released, and means beyond the operators control for removing each switch releasing means from her sole control and subjecting each of them to the combined control of the operator and the called line.

trunk in series to establish a connection with the called line, switch releasing means individual to each switch of the train, means controlled by the operator before the called line responds for operating each switch releasing means to release all the switches simultaneously, and means operated after the called line responds for transferring the switch releasing means from the absolute control of the operator to the combined control of the operator and the called line.

In witness whereof, I hereunto subscribe my name this 21st day of July, A. D. 1919.

RAY STOKELY.

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