US2398854A - Telephone system - Google Patents

Description

April 23, 1946. A. J. RAY

TELEPHONE SYSTEM Filed Oct. 21, 1945 s Shets-Sheet 1 m Y mm M J. 871.. mR m T 3E m Rom $TI; z :5 w, j o: E oQ i3. 250 mm; 6h 6:

m roxm ATTORNEY April 23, 1946.- A. J. RAY

lELIEiPHONfl SYSTEM 3 Sheets-Sheet 2 mmDNEm ma/ i comb Ffiled Oct. 21, 1943 INVENTOR. ARTHUR J. RAY

BY r

mmm-

ATTORNEY A. J. RAY TELEPHONE SYSTEM April 23, 1946,

Filed Oct. 21, 1943 s Sheets-Sheei s 20 wmm o 0 Ioxm r lw mlmm m mmm I E. I L

m Ioxm INVENTOR. ARTHUR J. RAY

ATTORNEY Patented Apr. 23, 1946 TELEPHONE SYSTEM Arthur .1; Ray, Chicago, IlL, assignor to Automatlc Electric Laboratories, Inc., Chicago,'Ill.,

a corporation of Delaware Application October 21, 1943, Serial No. 507,067

14 Claims.

The present invention relates to telephone systems in general, but is concerned more particularly with the use of voice amplifier repeaters in telephone connections.

It is the object of the present invention to provide automatic means for including a voice amplifier repeater in certain telephone connections established through the medium of automatic switches.

It is a feature of the present invention to provide a trunk repeater which is utilized in establishing telephone connections which mayor may not require voice amplifier apparatus and to determine whether the'amplifier is to be included in or excluded from the connection by the operation of the automatic switches involved in the connection.

It is a further feature of th invention to provide a trunk repeater which is selectable over either of two different paths and which controls the inclusion or exclusion of ,a voice amplifier repeater in the connection, depending upon the path over which the trunk repeater is seized,

It is a still further feature or the invention to provide facilities in a two-way trunk repeater of the above type for repeating supervisory signals in either direction over a connection.

Further features of the invention pertain to the particular arrangement of the circuit elements of the telephone system, whereby the above outlined and additional operating features are attained.

Novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, together with further objects and features thereof, will best be understood by reference to the following specification, taken in connection with the accompanying drawings, in which Figs. 1 to 3, inclusive, when placed end to end in the order named, illustrate a telephone system having incorporated therein the features of the invention as briefly outlined above.

Referring now more particularly to the operation of the system to set up different types of connections, a call originating on a line terminating in exchange A and intended for a line terminating in exchange C will first be considered. Assuming that a call is routed to the manual operators position in exchangeA, the operator attending this position may forward the call in the usual manner by plugging a cord circuit at her position into a jack terminating the trunk I90. When this trunk is seized in this manner a circuit is completed for energizing the battery feed relay I30 in the automatic exchange B over a circuit as follows: ground, lower winding of relay I30, winding I13 of the repeating coil RCI, contacts I24 and H3, positive conductor I02 of'the trunk line I90 through the cord circuit equipment, at the operators position in exchange A, negative conductor I! of the trunk line I30, contacts III and I22, winding III of the repeating coil RCI, upper winding of battery at contact I32 completes an obvious circuit for energizing the slowto-release relay 2I0. At contact I 3|, relay I30 opens a point i t complete circuit for relay 230 and at contact I33 it prepares a point in the circuit of conductor 30'! extending. to the selector 380 shown in Fig. 3.

As a result of the above-traced circuit for, relay 2| 0, this relay energizes and at contact 2I l prepares a circuit for relay 230; at contact 2I2 it opens a point in the circuit of the ri back-tone conductor I90; at contact 2 it disconnects the battery potential through resistance 2I3 from the test conductor 313; at contact 2I3 it places direct ground potential upon the test conductor 313 in order to busy the repeater circuit of Figs- 1 and 2 to other switches, such as selector 350, having access thereto; and at contact 2I5 it completes an obvious circuit for energizing the seizure relay 200.

Relay 200 upon energizing, at contacts 20I and 203 disconnects the battery feed relay 240 from windings I83 and I85 of the repeating coil RC2, and at contacts 202 and 204'it substitutes there- 'for the circuit including resistance 20I and the upper winding of relay 220. As a further result of the energization of relay 200, a circuit is completed at contacts 206 and 201 for energizing the line relay 3I0 of the associated selector 380 in series with the upper winding of relay 220. The circuit for energizing line relay 3I0 of selector 380 may be traced from ground, lower winding of line relay 3I0, contact 304, positive conductor 301, contacts I33 and 201, winding I85 of the repeating coilrRC2, contact 204, upper winding of relay 220, resistance 29I, contact 202, wind ing I83 of the repeating coil RC2, contact 206, negative conductor 300, contact'30 I, upper winding of line relay 3I0, to battery. Upon energizing, relay 3I01 prepares the selector 380 to receive impulses dialed bylthe" operator at exchangeA. I

As a further result of the energization of seizure relay 200, a circuit is completed at contact 205 for energizing the lower winding of relay 220. It will be recalled that in the abovetraced circuit for energizing lin relay 3I0 of the selector 380, the upper winding of relay 220 was included in this circuit and consequently its I upper winding is also energized. However, the magnetic flux set up in the upper winding of relay 220 at the present time opposes the magnetic flux set up by the circuit completed over thelower winding of the relay. Since the flux generated in the two windings of the1re1a-y oppose each other, relay 220 is prevented from energizing at this time. The repeater circuit disclosed in Figs. 1 and 2 is now in condition to repeat impulses transmitted by the operator at exchange A to the selector 380.

Responsive to the seizure of the trunk lines I90 by the operator at exchange .A, relays-I30, 1200, and 2I0 in the repeater circuit of Figs. 1 and 2 are energized in the manner described above. As a further result'of the seizure of the repeater circuit, the associated selector 380 is seized and the line relay 3I.0 thereof is energized over the previously traced circuit. Selector.3.80 now causes dial tone to be transmitted to the operator at .exchange A to .indicate that the selector 3.80 is in condition to respond .to impulses comprising the first digit. I

It will be assumed in the present instance that the operator at exchange A manipulates the dial, associated with her cord circuit, to transmit impulses indicative of the digit 5. Upon the first momentary interruption of the loop circuit including the battery feed relay I 30, the relay momentarily restores to normal, opening the previously traced circuit for the slow-to-release relay 2I0at contact I32, and at contact I3I it completes a circuit from ground, by way of contacts I3I and 2, through the winding of relay 230, to battery. Relay .230 energizes over this circuit and at contact 23I prepares a point in a locking circuit .for itself, and at contact 232 it completes a multiple circuit in shunt of the .upper winding of relay 220 and winding I83 of the repeating coil RC2 in order to improve impulse transmission to the selector 380. .Current flow in the upper winding of relay 220 is not reduced .suificiently when the multiple circuit is completed to cause the relay to energize over the circuit including its lower winding.

Due to the fact that relays .2I'0 and 230 are of the slow-to-release type, the momentary interruptions in their energizing circuits, responsive to the momentary deenergizaion of relay I30 .during impulsing, has no .efiect upon these relays and they remain operative during impulse transmission. At contact I33, relay I30 interrupts the above-traced loop circuit for line relay 3I0 in order to repeat the impulse transmitted by the operator at exchange A to the selector 380.

Accordingly, relay 3I0 follows the momentary interruptions under control of battery feed relay .I30 and thereby causes the wipers-32B to 322, inclusive, of the selector 380 to be raised in a vertical direction to a level in its associated banks corresponding to the digit dialled bythe operator at .exchange A. After the wipers have been raised to the desired level they .are automatically rotated over .the bank contact in search of an idle trunk line terminated in the selected level.

After the last impulse of the series of impulses constituting the digit 5 has been transmitted, relay !30 comes to rest in its energized position and again opens the circuit at contact I3] of the slowto-release relay 2.30.. .At contact I32, relay I30 again closes the circuit of relay 2| 0, and at contact I33 it again completes the l op c rcuit extending to the selector 380 in order to maintain line relay 3I0 in its energized condition. Relay 230 subsequently deenergizes and removes the multiple circuit including resistance 290 from the upper winding of relay 220 and the winding I83 of the repeating coil RC2.

The selector 380 of Fig. 3 is of the conventional Strowger type and includes a wiper shaft carrying the wipers 320 to 322, inclusive, and an associated set of bank contacts. The wiper shaft is adapted to be operated step by step in a vertical direction to position two wipers opposite one of the 10 levels in the associated bank, which level corresponds to the digit received by the .selector. Furthermore, the wiper set is adapted to be automatically rotated over the ten individual spaced contacts in any selector level. Since the Strowger type switch is well known in the art, it has been schematically shown and only such apparatus as is deemed necessary in carrying out the present invention has been shown. More particularly, the normal post springs, NPS including the contact 3I5, are so positioned that when the wiper shaft is operated to the 10th level the contact 3I5 is closed and remains closed during the time the wipers 320 to 322, inclusive, remain in any position on the 10th level. It should be noted, however, that the normal post springs NPS maybe mounted to be actuated on any desired level and that any number of sets of .normal post springs may be provided in order to accomplish the switch operation to be described hereinafter on any one or more levels of the associated set of contact banks.

In the present example, at the conclusion of the transmission of the digit 5, the wipers 320 to 322, inclusive, occupy a position adjacent the 5th level in the associated contact bank and shortly thereafter the Wipers are automatically rotated over the individual contacts in the 5th level of the bank in search of an idle trunk line extending to exchange C. It will be assumed that the trunk line 3&0 is idle and that the wipers 320 to 322, inclusive, come to rest in engagement with bank contacts 33I to 333, inclusive, terminating the conductors 334 to 336, inclusive, which are individual to the repeater 330 and the associated trunk line 340. When the test wiper 322 of the selector 380 encounters the bank contact 333 the rotary stepping action of the wipers 320 to 322, inclusive, is terminated and the switch through relay 300 is energized, in the well known manner, to extend the conductors 30B and 301 by way of contacts 302 and 303, Wipers 320 and 32I, and bank contacts 33l and 332 to the line conductor 334 and 336 extending to the repeater 330.

When the repeater 330 is seized over the abovetraced circuit it operates to cause ringing current to be transmitted over the conductors 3M and 342 of the trunk line 300 to signal the operator at exchange C and at the same time it functions to transmit a ring back tone signal over the calling end of the connection to indicate to the operator at exchange A that the connection has been extended and that the operator at exchange C is being signalled. The repeater 330 also operates to returnground potential over the test conductor 335 to maintain selector 380 in its operated position and to mark the repeater 330 busy to all other selectors, such as 380, having access thereto.

When the operator at exchange C answers the call, the repeater 330 functions to reverse the current flow over the circuit including conductors 3.34 and 336, 395 and 301, windings I83 and I85 of the repeating coil RC2 and the upper winding of relay 220. It has been pointed out above that the current flow in the circuits through the upper and lower windings of the thereby energized. Upon energizing, relay 220,.

at contact 22I, completes a circuit for energiz ing the battery reversing relay I20. Upon energizing, relay I20 at contacts I2I and I23 reverses the current flow over trunk I90 by reversing the. connection of battery and ground potential, through the upper and lower windings of battery feed relay I30, to the calling trunk I90; As a result of the reversal of current flow over trunk line I90 a signal is given to the operator at exchange A indicating to her that the operator at exchange C has responded to the call. The operator at exchange A may now converse with the operator at exchange C and for- Ward the necessary information as to the destination of the call. The talking circuit between the operator at exchange A and exchange C includes the trunk line I90, contacts III and H3, contacts I2I and I23, windings HI and I13 of the repeating coil ROI and the battery feed relay I 30, the battery feed relay I 30 providing the necessary talking current for the calling end of the connection. Voice currents received in the lefthand windings Ill and I13 of the repeating coil RCI are induced into the righthand wind-- ings I14 and I15 of the repeating coil and are extended by way of contacts "SI and IE4 to the lefthand windings IBI and I82 of the repeating coil RC2.

into the righthand windings I83 and I05 and thereby repeated by way of contacts 206 and 201, contact I33, conductors 303 and 301, contacts 302 and 303, wipers 320 and 32I, contacts 33I and 332, conductors 334 and. 336, through the repeater 330, conductors 3M and 342 of the trunk line 340, to the operator at exchange C.

When the operator at exchange C has ascertained the number of the called subscriber she inserts her cord circuit into the jack of the wanted subscribers line and signals the wanted subscriber. When the called subscriber responds, the operator at exchange C operates a key associated with the cord circuit to extend the talk- Voice currents received in the left-, hand windings of repeating coil RC2 are induced.

at the switchboards included in the above described connection to signal one another without releasing the established connection. In order to describe the operation of the circuits involved in the established connection in the event that an operator at one exchange recalls the operator at the other exchange, it will be assumed that the operatorat exchange A desires to signal the operator at exchange C in order to get her back in on the established connection. By flashing a key associated with the cord circuit involved in the connection, the operator at exchange A causes the circuit of relay I to be momentarily opened and closed a number of times. Each time relay I30 restores to normal a:

circuit is completed for energizing slow-to-release 230 at contact I3I, and at contact I 33 the loop circuit including conductors 306 and 301 is opened. In response to the momentary interruptions of the loop circuit including conductors 306 and 301 the repeater 330 functions in the well known manner to cause a flashing supervisory signal to be transmitted to the operator at exchange C to indicate to the operator thereat that the operator at exchange A desires to converse with her. The repeater 330 also maintains ground potential on conductor 335 to prevent the release of selector 380. As a' further result ing circuit through the cord circuit at her position of switchboard to the called subscriber.

When the operator at exchange A has ascer tained that the called subscriber in exchange C has responded to the call, she operates a key associated with her cord circuit to complete the connection between the calling subscriber in exchange A and the called subscriber in exchange C. The connection between the calling subscriber and the called subscriber is completed and they may now converse.

It will be noted that in the above described connections the voice repeater I80. schematically shown in Fig. 1, has been lay-passed because the transmission loss in connections established between the subscribers in exchange A and the subscribers in exchange C is not surficient to warrant the inclusion of a voice amplifier repeater.

It may be necessary at times for the operators of the momentary interruptions in the loop circuit including conductors 306 and 301 the cir cuit of the upper winding of 220 is also interrupted. However, due to the fact that the circuit through the lower winding is maintained, the relay does not restore at this time. Furthermore, the shunt circuit completed for the upper winding through thecircuit including contact 232, responding to the energization of relay 230, and including winding I83 of repeating coil RC2, has a tendency to maintain relay 220 in its energized position. When the operator at exchange C answers the flashing signal the connection between the operators in exchanges A and C is completed and they may converse with one another. When the operators disconnect from the cord circuits the conversational connection between the calling and called subscriber is again completed.

In the event that the operator at exchange .C desires to signal the operator at exchange A in order to get the latter operator back in on the established connection, she may do so bymomentarily operating a. key associated with her cord circuit. In responseto the momentary operations of the key, the repeater 333 momentarily reverses the current flow over the loop circuit including conductors303 and 301 a number of times. Each time the current in the loop circuit is reversed the relay 220 deenergizes due to the fact that the current flow in the upper winding of the relay opposes the current flow through the lower winding of the relay. Each time relay 220 restores to normal it opens the circuit of the reversing relay I20 at contact 221. Each time the circuit of relay I20 is opened the relay restores to normal and at contacts I 2I to I24, inclusive, reverses the current flow over the trunk I 90.v The reversals in current flow over trunk I causes the supervisory signal assothe conversation is completed the operators disconnect from the established connection and thereby reestablish the conversational connection between the calling and called subscribers.

When the conversation between the subscribers has terminated and the called subscriber hangs up his receiver, the operator at exchange C is thereby given a disconnect signal. In order to breakdown the established connection the operator at exchange C removes the plug of her cord circuit from the trunk 340, thereby causing the repeater 330 to operate and again reverse the current flow over the loop circuit including conductors 306 and 307. Due to the current reversal over conductors 306 and 301, thecurrent flow through the upper winding of relay 220 is again reversed and opposes the current flow through its lower winding. Consequently, relay 220 restores to normal and at contact 22I it opens the energizing circuit of the battery reversing relay I20. Relay I20 restores to normal and at contacts I22 and I24 again reverses the current flow over the trunk I90, thereby giving a disconnect signal to the operator at exchange A. The operator at exchange A may either test the trunk I90 to ascertain whether or not the operator at exchange C is still on the called end of the connection, or she may converse with the calling subscriber in exchange A to ascertain whether or not that subscriber has completed the conversation or desires to extend a new call. Upon ascertaining that the connection is to be disconnected the operator at exchange A removes the cord circuit from the trunk I90, thereby opening the previously traced circuit for maintaining battery feed relay I30 energized, Relay I30 restores to normal and at contact I33 opens loop circuit including conductors 300 and 307 and the selector 380, thereby causing repeater 330 to restore to normal. Repeater 330 in restoring removes the ground potential from the test conductor 335, thereby causing the selector 380 to release and restore its wipers 320 110322, inclusive, to normal. As a further result of the deenergization of battery feed relay I30, the energizing circuit of release relay 2E0 is open at contact I32 and at contact I3I it completes a circuit by way of contact 2H for the relay 230. Slow-to-release relay 2I0 subsequently returns to normal and at contact 2I3 removes the ground potential from conductor 313, thereby removing the busy condition placed on the trunks 35I and 352, at contact 2M it replaces battery potential, through resistance 2I6, on conductor 313, thereby indicating to selectors having access to the repeater that the circuit is in condition to be seized. As a further result of the deenergization of relay 2I0, the circuit of relay 2% is open, which relay upon restoring to normal, connects the battery feed relay 240 by way of contacts 201 and 203 to further prepare the repeater of Figs. 1 and 2 for seizure by way of selectors, such as selector 350. As a further result of the deenergization of relay 200, the energizing circuit for the lower winding of relay 220 is open at contact 205 and at contacts 206 and 20'! additional points in the circuit of conductors 306 and 301 are opened. The repeater of Figs. 1 and 2 is now completely restored to normal and is'available for new calls.

If the calling party releases the connection first, the operator at exchange A. is signalled thereby and responsive to this signal she removes her cord circuit from the trunk I90. When the cord circuit is removed from the trunk I90, re-

lay I30 restores to normal thereby causing the subsequent restoration of relays 2"], 200 and 220 in the order named. As a result of the restoration of relay 220, the circuit of relay I20 is opened at contact 22 I. Relay I20 restores to normal but has no function to perform atthis time since the cord circuit at the operators position at exchange A- has been removed from the trunk I90. As a result of the restoration of relays I30 and220 the loop circuit, including conductors 306 and 301, is opened, thereby causing the repeater 330 to restore to normal. In restoring the repeater 330 reverses the current flow over conductors 34I and 3 52 and causes a disconnect signal to be given to the operator at exchange C. As a further result of the restoring of repeater 330, ground potential is removed from conductor 335, thereby causing the selector 380 to restore its wipers 320 to 322, inclusive, to normal. The operator at exchange C now removes the cord from the trunk 340 and from the called subscribers line. The repeater shown inFigs. 1 and 2 is now in condition tobe utilized in new calls.

In the above described connection the voice repeater Iliii'was not required because the transmission loss in connections established between local subscribers in exchange A and local subscribers in exchange C is not sufficient to require the inclusion of a voice amplifier repeater.

In the connection about to be described, it will be assumed that the call received by the operator at exchange A is a toll call from a distant exchange. When a toll call is received by, the operator at exchange A for a subscriber in exchange C or for a subscriber in an exchange located beyond exchange C she is required to dial the digit 0 instead of the digit 5, as previously described. The operation of the apparatus as a result of the dialling of the digit 0 causes the voice amplifier repeater I30 to be included in the established connection in order to amplify the speech transmitted over the connection.

More specifically, when a toll call is received by the operator at exchange A she inserts her cord circuit into the trunk line I90, thereby causing the energization of thebattery feed relay I30 in the usual manner. At contact I32, relay I30 completes an energizing circuit for the slow-torelease relay 2H0 and at contact I33 it prepares a point in the loop circuit including conductors 330 and 307. Relay 2), upon energizing, at contact 253 extends ground by way of contact I52 and conductor 373 to mark the repeater busy in the banks of selectors, such as selector 350 having access thereto. As a further result of the energization of relay 2I0, a circuit is completed at contact ZIES for energizing relay 200. Upon energizing, relay 200, at contacts 2M and 253, disconnects relay 2410 from the righthand windings of the repeating coil RC2 and at contacts 202 and 20 connects the upper winding of relay 220 in series with resistance 29! to the righthand windings of repeating coil RC2. As a further result of the energization of relay 200, a circuit is completed for the lower winding of relay 220 at contact 205 and at contacts 200 and 20? it completes a loop circuit by way of conductors 386 and 38'! for energizing line relay 3i0 in the selector 380. The circuit for energizing line relay 3H3 may be traced as follows: ground, lower winding of relay 3E0, contact 300, conductor 301, contacts I33 and 201, righthand winding I of the repeating coil RC2, contact 234, upper winding of relay 220, resistance ZEII, contact 202, upper righthand wind- ,this time.

rent flow through the lower winding thereof,

thereby preventing relay 220 from energizing at As a result of the seizure of selector 380 in the above described mannerdial tone is transmitted to the operator at exchange A indicating that the connection is established with a selector and that it is in condition to respond to impulses transmitted from the. dial associated with the cord circuit at the operators position.

Since the connection being described is one requiring the inclusion of the voice ,repeater I80 the operator at exchange A manipulates her dial to transmit impulses indicative of the digit 0. Relay I 30 responds to the impulses transmitted in the manner previously described and at contact I33 repeats the received impulses to the selector 380. Upon the first'deenergization of the relay I30, a circuit is completed at contact I3I for energizing the slow-to-release relay 230, which relay, upon energizing at contact 232, closes a multiple circuit including resistance 290 across the upper winding of relay 220, resistance 29I and winding I83 of the repeating coil RC2 in order to improve impulse transmission to the selector 380. Relays 2I0 and 230 remain energized during the time the impulses constituting the digit are being transmitted to the selector 300. After the last impulse of the series is transmitted, relay I30 comes to rest in its energized position, thereby opening the circuit of relay 230 which relay upon restoring removes the multiple circuit including resistance 290 from across the circuit including the upper winding of relay 220, resistance 290 and repeating-coil winding I83.

In response to the ten impulses constituting the digit 0," line relay 3I0 of the selector 380 causes the wipers 320 to 322, inclusive, to be raised in a vertical direction to the th level of its associated bank contacts. When the shaft carrying the wipers 320 to 322, inclusive, is raised to the 10th level, the normal post springs, NPS, are operated to close contact 3I5. Shortly after the wipers of the switch has been raised to the 10th level they are automatically rotated over the individual contacts in the level in search of an idle trunk line extending to a repeater, such as repeater 330. It will be assumed that the wipers 320 to 322, inclusive, have been rotated over the 10th level of its associated bank and have come to rest in engagement with bank contacts 325 to 321, inclusive, terminating conductors 334 to 336, inclusive, of repeater 330. i 3

As-a result of the closing of contacts 3I5 by the normal post springs NP'S a circuit is, completed from ground, contact 3I5, conductor 305, winding of relay 210 to battery. Relay 210 energizes over the above traced circuit and at contact 21I prepares a point in the circuit of cut-in relays I40 and I60, which circuit will be completed subsequently to include the voice amplifier repeater I80 in the established talking connection.

As a result of the seizure of conductors 334 to 338, inclusive, by the selector 380, a circuit (not shown) is completed for relay 300 whereby the loop circuit, including conductor 303 and 301, is extended by way of conductor 334 and336 to control the operation of the repeater 330. When the repeater 330 isseized in the above described manner, ringing current is extended by way of conductor MI and 332 over the trunk 340 to signal the operator at exchange C. Asa further result of the seizure of repeater 330, ground potential is returned by way of conductor 335 to maintain the selector 380 in its operated position.

In order to answer the call received over trunk 340 the operator at exchange C inserts the plug of a cord circuit at her position into a jack terminating trunk 340 thereby causing the repeater 330 to reverse the direction of current flow over the loop circuit including conductors 334 and 336 and conductors 306 and 301. Due to the fact that the current flow over the loop circuit, including conductor 386and 301, is, reversed, the current flow, through the upper winding of relay 220 is also reversed and is now in such a direction that it aids the current flow through the lower winding of the relay. Relay 220 now operates and at contact 22I completes an energizing circuit for battery reversing relay I20. Relay I20 operates .and at contacts I2I and I23 reverses the current fiow over trunk I90 to thereby signal the operator at exchange A that the operator at exchange C has answered the call. As a further result of the energization of relay I20 a circuit is completed at contact I25 for operating the cut-in relays I40 and I60 as follows: ground, contacts 2I3, I52, I25 and 2H, windings of relays I60 and I40 to battery. As a result of the energization of relay I40 a circuit is completed at contact I45 for locking relays I40 and I60 in .an energized condition independently of the circuit including contact I25 of relay I20. As a further result of the energization of relay I40, contactsl42 and I44 are opened to disconnect the pad circuit, .including resistance I 16 and condenser I11, from across the terminals I88 and I81. of the voice repeater I80, and at contacts I4Iand I43 relay I40 connects terminals I86 and I81, of the voice repeater I80, to the righthand windings I14 and I15 of the repeating coil RCI. As a result of the energization of cut-in relay I60, the pad circuit, including resistance I18 andcondenser I19, is disconnected from terminals I88 and I89 of. the voice repeater I at contacts I63 and I66, and at contacts II62 and I the terminals I88 and I89 of the voice repeater I80 are connected to the lefthand windings I8I and I82 of the repeating coil RC2. As a still further result of the energization of relay I60, contacts I6I and I64 are opened to disconnect the circuit normally shunting the voice repeater I80 from the circuit including the righthand windings of the repeating coil RCI and theleft- .hand windings of repeating coil RC2.

The operator at exchange A may now converse with the operator at exchange C over a circuit including the voice repeater. I80 and informs the operator at exchange C of the number of the wanted subscriber. The operator at exchange C extends the connection to the wanted subscriber's line and after obtaining the wanted subscriber operates a key associated with her cord circuit to disconnect herself from the connection through to the wanted subscriber. When the connection is obtained with the wanted subscriber, the operator at exchange A operates a key associated with her cord circuit to complete the toll connection from the calling subscriber to the called subscriber. H 1

At this time it maybe well to mention that if the connection'just described was originated by a local subscriber in exchange A and wasto be completed to a subscriber in an exchange beyond exchange C the transmission loss would be too great to permit conversation to take place without the inclusion of a voice repeater, The operator at exchange A would, therefor, dial the digitI0,. in.- stead otithe' digit in establishing the- 'connectlonin order to include the voice repeater I80; in the connection. in. the same manner as has been described abovein connection with the. toll call received by the operator inexchangeA for asubscriber in exchange C.

The operation of the circuits in order to recall the operators-- at the two exchanges back into the established connection is the same as has been described: hereinbefore.

When the conversation between the calling toll subscriber and the local subscriber inexchange C hasbeen-terminated the operator at exchange A removes the plug of her cord circuit from the trunk ISO-whereupon battery feed relay I30 restores tonormal." At contact I33, relay I30 opens the loopcircuit including conductor 306 and 301, thereby causing the repeater 330 to transmit a disconnectsignal to the operator at exchange C. As a further result of the restoration of relay I30, the-circuit of; relay 21 0 is opened at contact I32 whereupon relay 210 slowly restores to normal. lilpo'n deenergizing, relay 24 0 at contactZ I 3, opens the locking circuit for relays I40 and I60. Relays. I40 and I60 restore to normal, thereby reconnecting thepad circuits to terminals I86 and I31; and to. terminals I88 and I89. of the voice repeater I80 in: order to prevent the voice repeater L80 from oscillating during the period of timeitis not included inthetalking connection. Asa. further result ofthedeenergization of relay 2:10, thecircuit of relay 20,0isopen at contact 2 I 5. Relayi200 restores. tonormal, thereby opening a further point in the-loop circuit extending to the repeater 330 atcontacts 206 and 20-land at contacts 2M and 203- it. connects the winding of relay Z40;to-windi ngs I83: and I85 of the repeating coil 'RCL. At contacts 202 and 204, relay 200 disconnects the circuit including resistance 291 and the-upperwinding of relay 220 from the repeatingccoil. RC2 and atcontact 205 it opens the circuit; for the lower winding of relay 220-. Relay 220 restores toznormal and: at contact 22-I it opens thescircuit of. relay I20 which also-restores;

As alresultof the restorationof relays I20, I30, I40, L60, 200.; 2120 and 220 the repeater circuit shownin Figs 1: and 2 is restored to normal: It should:beunderstood'that responsiveto the-restoratiorrof: relay 210 the ground potential placed on conductor 3il3lat contact 2l3 to-make therepeater busy to.selectors, such asselector 350, having access thereto-is. replaced by battery through resistance 21:6; to. mark. therepeater idle tosuch selectors.

Responsive to the opening oi the loopcircuit including conductors 306 and 301, due tothe restoration of relay I30, the repeater 330 restores to: normal and thereby removes the holding ground. potential from conductor 335. When ground; potential is removed from conductor 335 the selector 380 releases and restores its wipers 320. to 321,. inclusive, to normal. It should be understood that therepeater 330-and the selector 38llz'willi restore to normal before the repeater of Figs. 1 and 2lhave completely restored. As a result.oftherestoration of the .wiper shaft in a vertical direction, the normal post springs, NPS, are: restored and contact 3I5 is opened, thereby causing relay 24.0. to restore. The equipment is nowrcompletely restored to normal and is available; for new calls.

ithe; op rator at. exchange C- should disconnectflrslzirelay 220,-would deenergize-and thereby ause e ay I20 to restore-and rererse thecurrent merc es;

scribed to. signal. the.v operator at. exchange. A. Subsequent release. of the apparatus being under control. Of, the-woperator at exchange A as described above.

From the foregoing itshould be understood that two classes of connections may be estab-. lished. under control or the. operator at exchange A. One: class; of: connection including. the, voice repeater I80 in the-transmission circuit. in order to amplify th voice currents transversing the transmission circuit in both direction and the other class of connection excluding, the voice repeater I80 from, the transmission circuit. Furthermore, it. should be understood that the value of the digit dialled by. the operator at exchange A in extending the connections determines whether or not the normal postsprings, NPS, in the selector 380 will operate and cause the voice repeater I80 to be included in the transmission circuit. The extension of the connection described hereinbeforeas a result of dialling the digit 5, did not cause the operation of normal post springs, NPS, and. the voice repeater I80 was excluded from, the transmission circuit. However, the extension of the comiection described hereinbefore asa result of dialling the di it 0 cause the operation of normal post springs, NPS, and the'voice repeater was included in the transmission circuit;

A description will now begiven of the operation of the system when a call is initiated by a local subscriber in exchange C for a local subscriber in exchange A. When a local subscriber in exchange C initiates a call, the operator at the switchboard thereatanswers the call by inserting one end. of her cord circuit into the calling line jack and after receiving the number of the called subscriber she inserts the other end of the cord circuit into the jack terminating trunk 340. When the tr-unk 340 is seized in the above described manner; the repeater 330 operates to extend theconductors- 3M and- 342 of the calling trunk 340- by way of trunk line 343 to the Strowger type selector-350. As a further result of the seizure of repeater 330, test conductor 335 is grounded in order to busy the repeater 330 in the banks of: selectors, such as selector 380, having access thereto. As a result of the seizure of selector 350, dial toneis transmitted back over trunk 343 to the operator at exchange C to indicate that the selector'isin condition to receive dialledimpulses.

Since the operator at exchange C is. aware of the fact that the call to be transmitted is for a local subscriber in exchange Ashe manipulates the dial associated withthe cord circuit at her switchboard to transmit impulses indicative of the digit 8. The selector 350 responds in the well known manner to raise its wipersin a vertical direction totheeight level of its associated set ofbank contacts and automatically rotates its wipers over the individual contacts in the eight level in search. of an. idle trunkline extending to a repeater, such as a repeater disclosed in Figs. 1 and 2. It. will be assumed that in the present instance the wipers of. the selector 350 have come to rest in. engagement with the trunk line 351 comprising the conductors 360,,36I, and 362. The idle condition of the trunk line 35I is indicated by the battery potential applied thereto by way of resistance 2I6, contacts 2M and I52, conductor 313 and conductor 362. Whenthe test wiper ofthe selector 350' engages the. bank contact in itsassociated set of contacts terminating the conductor362, a circuit is completed in the selector 350 for extending the loop circuit, including conductors 34I and 342, from the operators switchboard, through repeater 330, trunk line 343, selector 350, conductors 360 and 36L to the windings of relay 240. The battery feed relay 240 energizes over the loop circuit which may be traced as follows: ground, lower winding of relay 240, contact 263, winding I85 of the repeating coil RC2, contact 265, conductor 3'I 4,conductor 35I of trunk line 35I, selector 350, trunk line 343, repeater 330, conductor 342 of the trunk line 340, through the operators cord circuit and returning by way of conductor 3 of the trunk 340, repeater330, trunk 343, selector 350, conductor 350 of trunk lin 35I, contact 263, winding I83 of the repeating coil RC2, contact 20I, upper winding of the batteryfeed relay 200, to battery. Relay 240 upon energizing over the above traced circuit, completes a circuit, at contact 242, for energizing relay I50 and at contact 20! it also completes a circuit for energizing the battery reversing relay Battery reversing relay I20 energizes over the above traced circuit and at contacts I2I and I23 reverses the connection of battery and ground potential throughthe winding of relay I30 to conductor l-9I and I92 of trunk E30. Relay I20 at contact I25 prepares a circuit for the cut-in relays I and I30 but this circuit is of noefiect since the connection being described does notrequire the inclusion of the voice repeater I80.

As a result of the energization of relay I50, a circuit is completed by way of contact I55 and 238 for grounding the ringing machine start conductor 292 to start the ringing machine in operation. As a further result of the energization of relay I50, ground potential is extended by Way of contact E53, conductor 313, and conductor 362 for ,inaintaining the selector 350 and the repeater 330 in operated condition. As a, further result of the energization of relay I50, batterythrough resistance 2I6 is disconnected from conductor 353 at contact I52. At contact I54, relay I50, upon energizing, completes an energizing circuit for relay 250 in multiple with an energizing circuit for ringin relay H0. At contact I5I, relay I50 also connects the ring-back tone conductor I96 by way of condenser I9l, contacts I51, 2I2, 233 and 253 to conductor 330 in order to indicate to the operator at exchange C that the operator at exchange A is being signalled.

Relay 250, upon energizing over the above traced circuit, prepares a locking circuit at con tact 25I for relay 230. At contacts 252 relay 250 prepares a circuit for battery reversing relay 260 and at contact 253 it opens a point inthe circuit of the deenergized seizure relay 200.

In response to the energization of ringing relay H0, contacts H2 and II 4 are closed whereupon direct generator is extended by way of conductor I94, contact H4 and trunk conductor I92 and simultaneously therewith battery potential is extended by way of resistance I93 and contact II2 to trunk conductor I! for thepurpose of ignalling the operator at exchange A. As a further result of the energization of relay IIO direct gen- When the direct generator is extended to the upper winding of relay I00, the-relay energizes and at contact IOI completes a locking, circuit for itself from ground at contact I54. As a further result of the energization of relay E00 the circuit for the slow-to-release ringing relay I I 0 is opened at contact 02. Relay H0 is madeslow-to-ra lease in order to make certain that the direct generator I90, and resistance battery are connected to conductors I92 and ISI, respectfully, for a sufficient period of time to signal th operator at exchange A. Ringing relay IIO subsequently restores to normal, thereby opening the signallingcircuit at contacts II 2 and H4, and

extending the conductors I9I and I92 through to the upper and lower windings of the battery feed relay 30 at contacts III and H3. As a further result of the deenergization of the ringing relay H0, direct generator is removed from the upper winding of relay I00 at contact II5. No further operations take place in the repeater in exchange B disclosed in Figs. 1 and 2 until the call is answered b the operator at exchange A. a When the operator at exchange Aanswers a call by inserting one end of her cord circuit into the jack terminating trunk, I90 a loop circuit is completed for energizing the battery feed relay I30 as follows: ground, lower winding of relay I30, winding I13 of the repeating coil RCI, contact I23 of the energized battery reversing relay I20, contact III, conductor I SI of trunk I30 through the cord circuit at the switchboard in exchange A and returning by way of conductor I92 of trunk I90, contact II3, contact I2i of the energized battery reversing relay I20, winding III of the repeating coil RCI, upper winding of relay I30 to battery. Relay I30 energizes over the above traced circuit and at contact I32 completes an energizing circuit for the slow-to-release relay 2I0 in multiple with the battery reversing relay 230. The closing of contact I33 byrelay 30 has no function to perform in this typeof connection because the circuit extending to the selector 380 is not closed at contacts 206 and 207 of the seizure relay 200.

Responsive to the energization of battery reversing relay 260, contacts 262 and 230 are closed simultaneously with the opening of con tacts 263 and 265 whereupon the current flow over conductors 360 and 36I is reversed, thereby causing a signal to be given tothe operator at exchange 0, indicating that the wanted operator at exchange A has responded to the call. At contact 26I, battery reversing relay 250 opens a point in the incomplete locking circuit of relay 230; at contact 263 it prepares a circuit for energizing the cut-in relays I40 and I60 only in energized responsive to the operation of relay I30.

erator connected to conductorl94 is also extended by way of condenser I95 and contact H5 to the upper winding of re1ay'I00. It should be noted that 'at the time-ringing relay IIO connects di rect generatorto conductor I92 and resistance battery to conductor I9I that at its contacts III and H3 it disconnects the battery feed relay I30 from the conductor I9I and I92. I r i Upon energizing relay 2| 0, at contact 2, prepares a circuit for relay 230, at contact 212 it disconnects the ring-back tone conductor I from the calling trunk, and at contact 2H5 it prepares a point in the circuit of the seizure relay 200. The talking connection between the operator atexchange C and the operator at exchange A is now completed and the conversation may take place whereupon the operator at exchange wanted local subscriber in exchange A. As a result thereof the operator at exchange A inserts the other end of the cord circuit at. her position into the jack of the wanted subscriber's line and when the wanted subscriber answers the call the operator actuates a key in the cord circuit to complete the connection. The operator at exchange C may now actuate a key associated with her cord circuit in order to disconnect herself from the connection and complete the connection between the calling subscriber at exchange-C andithe called subscriber at exchange A. Trans.- mission battery is fed to the calling end of 'the trunk by way of the battery feed relay 240- and transmission battery is fed to the called end of the trunk by way of the battery feed relay I30.

The windings of the repeating coils RCI and RC2 inductively coupling the calling end of the trunk with the called end of the trunk so that conversation may be carried on between the calling and called subscribers.

If the operator at exchange C desires to recall the operator at exchange A she may do so by momentarily operating a flashing key at her-position thereby causing. the batteryfeed relay 240 to momentarily deenergize and energize a number of times. Each time relay 240 restores it opens the circuit of battery reversing. relay I20, at contact 24 I. The momentary interruptions of contact 242 has no effect on relay I50 because of the multiple locking circuit thereforcompleted by way of contact I55 and.281'. Each time relay I20. restores it reverses the current flow overitrunk I90 at contacts IZI to I24, inclusive,'thereby'sig nailing the operator at exchange A. When the operator atexchange A answers the flashing signal caused by the momentary current reversals over trunk I90 she may converse with the. operator at exchange C.

In the event that-the operator at exchange A desires to recall the operator at exchang-eC', she may do so by momentarily. operating a flashing key at her position, thereby causingthe battery feed relay I30 tov momentarily deenergize. and energize anumber of times. Eachtimethebattery feed relay I30 restores'it opensthe circuit of. battery reversing relayv ZBDI-and. release relay 2I0atcontact I32.and atcontact I3I- it completes an energizing circuit for relay 230-. Relays 2H] and 230 areslow. to. release relays and'do. not restore each time the circuit of the relays is opened. Each. time battery reversingv relay 260 restores it completes alocking circuitfor relay 230 at contact 26! and at contacts 252 to 205, inclusive, it reverses the current flow over con ductors 360 and 314. Current reversals in the circuit including conductors 360 and 314 causes the repeater 330-to function in they well known manner to transmit a flashing supervisory signal to the operator at exchange C to-indicate that the: operator. at exchange A desires to'converse with her. When the operator at exchange: C answers the flashing signal conversation between the operators maytake-place; It should-beinoted that when the operator at exchangeG answered the recall relays I30, 2I0and 260:11emain in their energized positions and relay- 230-subsequently restoresto normal.

When the conversation iscompleted, the operators disconnect from the established-connection and therebyreestablish the conversational connection between the calling andcalledSubscribers;

- When: the conversation betweenthesubscribers iscompleted they may hang; up; their receivers:

: A is: informed of the telephone number" of the The replacement of the receiver by the calling subscriber in exchange 0 causes asupervisory lamp, associated with the cord circuit in the "switchboard at exchangeC, to give a disconnect signal tov the operator; Uponreceipt of the disconnect-signal; the operator at the switchboard inexchange C breaks-down the connection by removing the plugs of the cord circuit from the calling linejack and'from the jack terminating the line 340;

Responsive to the removal of the cord' circuit from the: trunk 340 the repeater 330 functions to open-the loopcircuit" including trunk line 343, the: selector 350; the trunk line 350; and talking conductors 360 and 36I, whereupon the battery feed relay 240 restores to normal;

As a result of the above described restoration of battery feed relay 240' the circuit for battery reversing relay I2'0'-is= opened at-contact 2'41, and at contact 242 a point in the locking circuit of relay: Hill-is opened, but'the latter relay remains locked' -upover a circuit including contacts 261 and I 55; Relay" l 2'0-restoresto normal when its circuit is opened and contacts I2! and I23 are opened and simultaneously therewith contacts I22 and I24 are closed, thereby reversing the current flow over the trunk conductors I9I and I92 in order to give adisconnect signal to the operator at the switchboard in exchange A.

Upon receipt of the disconnect signal, the operator at the-switchboard in exchange A removes the cord" circuit from the jacks terminating the called line and the trunk I whereupon battery feed relay I30 deenergizes and restores to normal. Upon restoring to normal relay I30 completes a circuit for relay 230 at contact I31, at contact I32 it. opensamultiple-circuit including the windings of release relay 2H] and battery reversing re1ay'260,.andat contact I33 it opens a point in the incompleted circuit. including conductor 301. Battery reversing relay 260' restores to normal at this time, but since the calling end of the trunk includingconductors. 3M and 342 have been disconnected by the operator at exchange C, this relay has no function to perform at this time at contacts 262 to 265, inclusive. At contact 26I, however, relay 260,,upon re'storingcompletes a circuit from ground, contacts 261, 25I, and 23I, winding of relay 230 to battery, thereby locking relay 230in.its energized position after it is energizedresponsive to therestoration ofbattery feed relay I30. At contact 2'61relay 260, upon restoring, opens the lockingcircuit of relay I50, whereupon relay. I50 restores to normal.

Due to its slow-to-release characteristics, relay 2-10 is somewhat delayed in. restoring to normal after its energizing, circuit. is opened by the restoration of the battery feedrelay I30. Subsequently, however, relay 210 restores. to normal and. at. contact 2 opens the initialv energizing circuitoirelay. 230, andat contact 2-I2 it prepares ai-point-in theringeback tone circuit. At contact 213 relay- 2-I 0.-opensav pointinthe circuit for applying. ground potential to. conductor 3-13, and at contact. 214 it. prepares a point inthe circuit for connecting. battery through the resistance 2I-6 to conductor 313;

Relay I50is-a slow-to-release relay and is somewhat delayed. in restoring to. normal after its lockingv circuit is opened. responsive to the deenergizationof the battery reversing, relay 260. Subsequently, however, relay I50- restores: to normal whereupon a" point. in the ring-back tone. circuit is opened. at; contact; I5;I', ground potential is removedtfrom the tests-conductor 313 challenges the calling line in. order to determine at contact I53 whereupon the preceding selector switch 350 is caused to release and restore its wipers to normal. In addition, the repeater 330 is released and removes the ground potential from conductor 335 to indicate to selectors, such as 380, that the repeater 330 is available for further use. At contact I54 relay I50 opens the energizing circuit of relay 250 and simultaneously therewith it opens the locking circuit including the lower winding of relay I and finally at contact I52 it connects battery through resistance 2I6 to the test conductor 313 thereby marking the repeater of exchange B (Figs. 1 and 2) available in the banks of selectors, such as selector 350, for additional calls,

Relay I00 restores to normal when its locking circuit is open in the above described manner and at contact I02 again prepares a circuit for the ringing relay H0. Slow-to-release relay 250 subsequently restores to normal after its circuit is opened by the restoration of relay I50, and at contact 25I it opens the locking circuit for relay 230, which relay subsequently restores to normal. At contact 252, relay 250 opens a point in the incomplete circuit of relay 250, and at contact 253 it prepares a point in the incomplete circuit of seizure relay 200. The equipment involved in the connection established between the subscriber at exchange C and the subscriber at ex-.

change A has now completely restored to normal and is available for additional calls.

In the above described operation of the release of the equipment responsive to the termination of the connection it was assumed that the calling subscriber at exchange C restored his receiver first to terminate the connection. It will now be assumed that the established connection previously described between the subscriber at exchange C and-the called subscriber at exchange A was terminated by the restoration of the re-' ceiver by the called subscriber.

When the called subscriber at exchange A restores his receiver the supervisory lamp associated with the cord circuit at the switchboard in exchange A is illuminated to give the operator the disconnect signal. When the operator at exchange A receives the disconnect signal she removes the plugs of the cord circuit from the calling line and from the jack terminating the trunk I90 whereupon battery feed relay I30 restores to normal. Upon deenergizing, relay I30 completes an energizing circuit for relay 230 by way of contact I3I and the closed contact 2. Upon energizing relay 230 prepares an incomplete looking circuit for itself at contact 23L A further result of the deenergization of relay I30 the multiple circuit including the windings of relays 2I0 and 260 is opened at contact I32. As a result thereof relay 260 restores to normal and at contact 20 I completesthe locking circuit for relay 230 by way of contacts 25I and 23I. As a further result of the cleenergiz-ation of relay 260, contacts 262 and 264 are opened and simultaneously therewith contacts 263 and 205 are closed whereupon the current flow over conductors 360 and 314 is reversed, whereupon, through the medium of the repeater 330, a supervisory signal is given to the operator at exchange C indicating that the operator at exchange A has released the connection. As a further result of the deenergization of relay 260 a point in the circuit of the ringing machine start conductor 292 is closed at contact 268.

7 When the operator at exchange C receives the supervisory signal indicating the release of the connection by the operator at exchange A she 1 his receiver.

scriber requires no further service and hangs up whether or not the calling subscriber has replaced Assuming that the calling subhis receiver, the operator at exchange C then removes the cord circuitfrom the jack of the calling line and from thejack terminating thetrunk 340 whereupon thecircuit of the' battery feed relay 240 is opened and the relay restores to normal, in the-manner previously described.

1, Relay 240, upon restoring tonormaLat contact 24I opens the circuit of the battery reversing relay I20, and at contact 242 it opens the circuit of the slow-toerelease relay I50. Relay I20 restores to normal and at contacts I2I to I24, inclusive, reverses the current flow over conductors I9I and I92, but thisoperation has no; function to perform at this time because theoperator at exchange A has removed the cord from the trunk I90. Relay I50 subsequently restores. to, normal and at contact I53 removes ground potential from the test conductor 313; thereby releasing the selector 350 in the manner previously described. At contact I52 relay I50 againconnects battery through the resistance 2 I6 to the :test conductor 313 by way of the contact 214 inorder to mark the repeater in exchange 3. (Figs-1 and 2) available for additional calls. As a further result of the restoration ofrelay I50, the multiple circuit including the lower windingof relay I00. and relay 250 is opened at contact I54. Relay I00 restores to normal and at contact I02 again prepares a circuit of ringing relay -IIO.- Relay 250 subsequently restores to normal thereby opening the locking circuit of relay 230 at contact 25I, and at contact 252 it opens an'additional point in the circuit of relay 200, and finally, at contact 253 it prepares a point in the circuit. of the seizure relay 200.. The equipment involved in the connection established between the calling subscriber at exchange C and the called subscriber at exchange A has now been restored to normal and is available for additional calls. l

"From the foregoing descriptionit should be understood that when a call originated by a subscriber in exchange C for a local subscriber in exchange A the operator in setting up the connection dials the digit 8 and thereby operates the selector 350 to the eighth level in order to seize the repeater. in exchange B (Figs. 1 and 2) over the trunk line 35L When the repeater in exchange B (Figs. 1 and 2) is seized over trunk line 35I the connection established thereoverexeludes the voice repeater'IBEI. In the event that it is necessary to include the voice repeater I in the connection in order'to amplify th speech current traversing the connection, the repeater in exchange B may be seized over the trunk line 352 by the selector 350. The operation of the equipment in the establishment of a call requiring the inclusion of the voice repeater I80 will now be described.

It will now be assumed that a local subscriber in exchange C desired to establish a connection with a subscriber in an exchange located beyond the area served by exchange A. When the op erator at exchange C ascertains the number of the Wanted subscriber she inserts the plug of her cord circuit into'the jack terminating thetrunk line 340 whereupon the repeater 330 is operated to ground the test conductor 335 and thereby mark the repeater 330 busy in the banks of selectors having access thereto. 'Asa further result of the seizure ofrepeater 330 a circuit is completed by way of trunk line 343 for operating se- "lector 350. When the operator at exchange C receives the dial tone indication that the selector 350 is in condition to receive dialled'impulses she manipulates her dial'to transmit impulses indicative of the digit 0. 1

The selector 350 responds in the well known manner to raise its wipers to the tenth level of its associated bank contacts and to automatically rotate the wipers over the individual contacts in the bank in search of an idle trunk line extending to an idle repeater, such as the repeater in exchange B shown in Figs. 1 and 2. It will be assumed that the wipers of the selector 350 have come to rest on the bank contacts terminating conductors 310 to 312, inclusive, of the trunk 352.

The repeater is marked as idle in the bank of the selector'350 by the battery potential applied to the test conductors 313 by way of resistance 2I6, contacts2l4; I52, conductors 313 and 312. When the selector 350 seizes the repeater in the 1 above described manner aloop circuit is completed over the trunk line including the trunk conductors 310 and 3H whereupon the following circuit is completedzground, lower winding of battery feed relay 240, contact '203,'winding I85 winding of battery feed relay 240 to battery. Re-

lays 240 and 280 energize over the above traced circuit. Upon energizing, relay 240 completes an energizing circuit for battery reversing relay I20 and it completes an energizing circuit for relay I50; Upon energizing battery'reverse rela I20 reverses the current flow over the trunk conductors I9I and I9 2 at contact I2I to I24, inclusive, and at contact I25 it prepares a point in the circuit of the relays I40 and IE0. When relay I50 energizes it removes battery through resistance 2I6 from the test conductor 313 at contact I52 and at contact I53 it places ground potential on the test conductor 313 inorder'to maintain the selector 350 in its operatedposition. At contact I5I, relay I50 connects the ring-back tone 0011- r nector I98 to the calling end of the trunk in order to indicate to the operator at exchange C that the operator atfexchange 'A is about to be signalled. As a further result of the energization of relay I50 a circuit is completed at contactl55 for grounding the ringing machine start conductor 202 in order to start the ringing machine apparatus in operation, and at contact I54 it completes a multiple circuit for operating relays 250 and H0. 7

It will be noted that when ground potential is applied to the test conductor 313, responsive to the closure of contact-I 53, a locking circuit'is completed for the energized relay 280 by way of its contact 282 which contact was the only contact closed when therelay 28.0 was energized over a circuit including its upper Winding. Relay 288 now fully energizes and at contact 28I places a shunt around the circuit including the upper winding of the relay and at contact 283 it prepares a point in the circuit of the cut-in relays I40 andISIl.

Relay 250' energizes when its circuit is. completed at contact I54 and functions in the manner lqreviously described to 'preparercircuit atcoh:

' tacts and 252 and toop'en a point in the circuit of the seizure relay 200 at contact 253.

Ringing relay i it energizes in the manner previously described and causes the operatorat exchange A to be signalled. Direct generator from conductor I34 is also extended by way of condenser I95 and contact I I5 to the upper winding of relay E00. Relay IE3 energizes from the ringingourrent transmitted over this circuit. thereby completingta locking circuit'for its lower winding by way of contact IOI to ground at contact I54, and at contact I02 it opens the energizing circuit of. ringing relay H0. The ringing relay H0 is made somewhat slow-to-release to insurethe signalling of the operator at exchange A. Relay I I0 subsequently restores and disconnects resistance battery and direct generator from the trunk conductors I9I and I32 at contacts II2 and H4, and at contacts II I and II3 it extends the trunk ccnductor through to the upper and lower windings of the battery feed relay I30.

The operator at exchange A answers the call in the usual manner, by inserting the plug of a cord circuit into the jack terminating trunk I00 whereupon a circuit is completed for energizing the battery feed relay l30. Upon energizing relay I completes a multiple circuit at contact I32 for energizing release relay 2 I0 in multiple with the battery reversing relay 255. Relay 210 energizes and at contact 2 i 2 disconnects the ring-back tone conductor I35 from the calling end of the trunk line, and at contact 2! I it prepares a point in the circuit of relay 230.

Responsive to the energization of relay 260 current flow over conductors 3H and 314 is reversed by the closing of contacts 252 and 264 and the simultaneous opening of contacts 253 and 205. The reversal of current flow over conductors 31I and 314 causes the repeater 330 to function and transmit a supervisory signal over trunk 340 to indicate to the operator at exchange C that the operator at exchange A has answered the call. As a further result of the energization of relay 230, relays I and I60 are energized over the following circuit: ground, contact I53, conductor I13. contacts 256 and 283, windings of relays I60 and I40 to battery. Relays I30 and IE0 energize over this circuit and at contact I relay I40 completes a locking circuit for both relays in series from ground at contact I53, which circuit is independent of the previously traced circuit including contacts 265 and 283. Asa further result of the energization of relay I40 the pad circuit including resistance I16 and condenser I11 is disconnected from the terminals I85 and I81 of the voice repeater I 80 at contacts I42 and I44, and simultaneously therewith the terminals I85 and I81 of the voice repeater I80 are connected to the righthand windings of the repeating coil RCI at contacts I4! and I 43; 'As a result of the energizetion of, relay I60 the pad circuit including resistance I13 and condenser I19 is disconnected from terminal I88 and I89 of'the voice repeater I80 atcontacts I63. and I66Yand simultaneously therewith the terminals I88 and I89 are connected by way of contacts I 62 and I to the lefthand windings of repeating coil RC2. As a further result of the energization of relay I the righthand windings of repeating coil RCI are disconnected from the lefthand windings of repeating coil RC2 at contacts IEI and IE4. The voice repeater I is now connected in the talking circuit including the windings of repeating coils RCI andRC2. Conversatio-nbetween the-operator at exchange C-and the'operator at exchange;Amay

going trunk over a particular oneof said now take place in the manner previously described. T

Upon ascertaining the number of the wanted subscriber the operator at exchange A extends the connection by way of'asubsequentexchange (not shown) and the operator thereat completes the connection to the wanted subscriber in the wanted exchange. The operators included in the connection now release therefrom and conversation between the calling subscriber and the called subscriber may, take place with the voice repeater I 80 included in the circuit in order to increase the amplification of the voice currents traversing the connection.

The operation of the circuits involved in the connection in order to recall the operators at exchange A and C back intothe established connection is the same as has been previously described when a connection is originated by the operator at exchange C.

When the conversation between the calling and called subscriber has been terminated the: equipment involved in the connection is released in the manner described hereinbefore, it being noted, however, that the circuit of. relay 280 is not opened until ground potential is removed fromcenductor 313 by the restoration of relay I50.

From the foregoing description it will be understood that the operator in exchange C when originating a call may cause the voice. repeater I80 to be included in the connection by operating the selector 350 to the tenth level. Therefore, she is instructed to establish connections by way. of the tenth level of selector 350 whenever a local subscriber in exchange C desires to establish a connection with a subscriber in an exchange located beyond the exchange area served by exchange A, or whenever a subscriber located beyond the area served by exchange C initiatesa call for a subscriber located either in exchange A or in an exchange beyond the area served by exchange A. Furthermore, the operator at exchange is instructed to operatethe selector 356 to the eighth level whenever a connection is to be established between a local subscriber in exchange C and a local subscriber in exchange A. Accordingly, the voice repeater I80 associated with the repeater of Figs. 1 and 2 will be excluded from the connection established between local subscribers in exchange C and exchange A.

While the present invention has been described and illustrated as applied to a semi-automatic telephone system, it will be understood that various modifications may be made therein to apply the invention to either full automatic or full manual systems and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a telephone system, an automatic switch, an outgoing trunk line, said trunk line accessible to said switch over a plurality of paths, a repeater associated with said switch, an incoming trunk line terminating in said repeater, means controlled over said incoming trunk for operating said repeater and said switch to complete a connection from said incoming trunk to said outgoing trunk over any of said paths, a voice amplifier, a control circuit efiective when operated for including said voice amplifier in said connection, and means in said switch effective in they event said switch is operated to select said out- 151 paths for operating said control circuit.

2. In a telephone system, an incoming and an outgoing trunk line, a trunk circuit terminating said incoming line, an automatic switch having access to said outgoing line over two paths, means for controlling said trunk circuit and said switch for interconnecting said lines to complete a connection therebetween overeither of said paths, a voice .currentrepeater, means in said trunk circuitfor including said voice current repeater in said connection, and means in said switch for operating said last mentioned means only in the event said switch is operated toselect said outgoing trunk over a particular one or. said paths.

3. In a telephone system, an incoming and an outgoing trunk line, a trunk circuit terminating said incoming line, an automatic switch having access to said outgoing line over two paths, means for controlling said trunk circuitand said switch for interconnecting said trunk lines to complete a connection therebetween, a voice current amplifier, and means in said switch operated in the event said switch is operated to select said outgoingtrunk over one of said paths for controlling said trunk circuit to include said voice current amplifier in said connection.

4. In a telephone system, a first exchange, a tandem exchange, a second exchange, a trunk repeater in said tandem exchange, a trunk line 'from said first exchange terminating in said resaid trunk repeater controlled from said first exchange for operating said switch to select said second exchange trunk line over either of said paths, and means in said trunk repeater controlled by said switch for associating said voice current repeater with said trunk repeater only in the event said switch is operated to select said second exchangetrunk line over a particular one of said paths.

5. In a telephone system, a trunk repeater, a trunk line terminating in said repeater having two incoming branches, an outgoing trunk line also terminating in said repeater, means operated responsive to the seizure of said repeater over either branch of said incoming trunk line for transmitting a signal over said'outgoing trunk line, means in said repeater controlled over said outgoing trunk line for transmitting a signal over either of said incoming branchesand for completing a talking connection between either of said incoming branches and said outgoing trunk line, a voice amplifier, and means operated only in the event said repeater is seized over a particular one of said incoming branches for operatively connecting said voice amplifier to said talking connection.

6. In a telephone system, an automatic switch, a trunk repeater accessible to said switch over two paths, a voice current amplifier, means in said repeater controlled in one manner in response to the seizure of said repeater over one of said paths for associating said amplifier with said repeater, said means ineffective when said repeater is seized over the other of said paths so that said amplifier is not associated with said repeater.

7. In a telephone system, an incoming trunk line, an outgoing trunk line having a plurality of access paths, switching apparatus controllable over said incoming trunk line for interconnecting said trunk lines over. any of said Paths, said switching apparatus including a trunk circuit having a plurality of inductively coupled sections, a voice amplifier, means in said trunk circuit effective when operated for including said: amplifier in one of said sections, and control means op'erated'in the event said incoming trunk line is interconnected with said outgoing trunk line over a particular one of said access paths for operating said last mentioned means.

8. In a telephone system, a trunk line, a distant exchange terminating said trunk line, said trunk line being utilized for local calls to subscribers in said distant exchange or for toll calls to subscribers located in exchanges beyondv the area served by said distant exchange, switchin apparatus having access to said. trunk line over two paths, means for operating said switching apparatus to seize said trunk line over either of: said paths to extend connections over said trunk line to said distant office, a voice amplifier, and means in said switching apparatus operated in the event said trunk line is seized over a particular One of said paths, to extend a toll connection through the medium of said distant ofiice, for including said voice. amplifier in said connection, said last mentioned means rendered inoperative in the event said trunk line is seized over the other of said paths to extend a local connection to a subscriber in said distant oflice.

9. In a telephone system, an incoming, trunk line, an outgoing trunk line having two pathsof access, a trunk circuit, means for interconnecting said lines including said trunk circuit, a voice amplifier, means in said trunk circuit for including said voice amplifier in said connection operated only in the event saidoutgoing trunk is selected over a particular one of said paths of ac- C655.

10. In a telephone system, a trunk circuit, a voice amplifier, means for establishing a talking circuit through said trunk circuit in either direction, cut-in means for including saidamplifier in said talking circuit, a circuit independent of the talking circuit established through said trunk circuit in one direction for operating said cutein means, and means included in the talking circuit established through said trunk, circuit in the opposite direction for controlling said cut-in means.

11. In a telephone system, a trunk circuit, a voice amplifier, an outgoing trunk over which connections are established through said trunk circuit, incoming trunks over which connections are established through said trunk circuit in the opposite direction, cut-in means for including said voice amplifier in the connections established through said trunk circuit, means for controlling the operation of said cut-in means responsive to a connection established over said outgoing trunk, and means included in one of said incoming trunks for operating said cut-in means each time a connection is established through said trunk circuit in said opposite direction over said one incoming trunk.

12. In atelephone system, a trunk circuit, a voice amplifier, means for establishing talking connections including said trunk circuit, means for cutting said amplifier in and out of said talking connections, means operated responsive to a talking connection being established throughsaid trunk circuit in one direction for operating said cut-in means, and other means operated responsive to. the establishment of a talking connection through said trunk circuit in th opposite direction for operating said cut-in means.

13; In a telephonesystem, a two-way trunk circuit, means for establishing telephone connections. including said trunk circuit, a two-way voice amplifier, means in said trunk circuit operable to out said amplifier in and out of said trunk circuit, means operated only in the event a connection is established through said trunk circuit in one direction for controlling the operation of said cut-in means, and means operated only in the event a connection is established through said trunk circuit in the opposite direction for controlling the operation of said cut-in means.

14. In a telephone system, a two-way trunk circuit, means for extending talkin connections over the trunk circuit in either direction, a voice amplifier, means for inserting the said amplifier into certain of said talking connections, means for determining whether the amplifier will be inserted into connections extended in one directiondependent upon theone of a plurality of incoming paths over which the trunk circuit is seized, and means for determinin whether the amplifier will be inserted into connections extended in the other direction over the trunk circuit dependent upon the one of a plurality of paths over which the connection is extended beyond the trunk circuit.

ARTHUR J. RAY.

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