US1800321A - Telephone system - Google Patents

Description

A ril 14, 1931. N. H. SAUNDERS ET AL TELEPHONE SYSTEM Original Filed April 16, 1928 5 Sheets-Sheet l MQQEQEKR -ITLUETL2U'!" 5 Norman H 5 aun ders Elarence E.Lumax April 1931- N. H. SAUNDERS ET AL 1,800,321

TELEPHONE SYSTEM Original Filed April 16, 1928 5 Sheets-Sheet 2 nuan or s Narman H.5aunder's Elar'euca E.Ln max M 4* 1 Wu April 14, 1-931. N, SAUNDERS ET AL 1,800,321

TELEPHONE SYSTEM Original Filed April 16, 1928 5 Sheets-Sheet 5 m Imreniur Nurmau H. Saundars E Zar encsE Lumax N H, SAUNDERS ET AL, 1,800,321

April 14, 1931.

TELEPHONE SYSTEM '5 Sheets'Sheet Original Filed April 16, 1928 QQ E i b R. I N 3% \R 9% 5w fiw Irma-n ur's Norman H. Saunders Elareuce E.LDT1'L&X

April 14, 1931. N. H. SAUNDERS ET AL 1,300,321

TELEPHONE SYSTEM Original Filed April 16, 1928 5 Sheets-Sheet 5 Imreu 0P5 Norma-n .Eaun ars lavenceELnmax Patented Apr. 14, 1931 OFFICE NORMAN H. SAUNDERS, 0F I-IOIVIEWOOIJ, AND CLARENCE I]. LOMAX, OF OAK PARK,

ILLINOIS, ASSIGNORS T0 RESERVE HOLDING GOMPZLNY, OF KANSAS CITY, MISSOURI,

trnnnriacnn sYs'rnM Application filed April 16, 1928, Serial No. $370,188. Renewed September 15, 1930.

v The present invention relates to telephone systems in general, but is concerned more particularly with semi-automatic telephone systems, and the main object, broadly stated, is the production of a semi-automatic telephone system wherein a common group ofsende'rs may be'used by semi-automatic operators in a centralized exchange in setting up connections from local lines and in setting up connections from lines of remote semi-automatic exchanges.

Another object is to provide distributing apparatus at a semiautomatic operators switchboard, which operates in conjunction with sender selectors for connecting the operators equipment automatically with any sender whichhasb'een selected by a sender selector so that'the operator may ascertain the desired number and operate a sender to control the automatic switches to'set up the desired connection.

- A further object of the invention is the production of suitable arrangements, efi'ee tive in connection with calls set up in a remote exchange by an operator over an operating trunk, controlled from the operating point over the operating trunkto disconnect the operating trunk from'the established connection and to place such connection under the control of the calling subscriber without momentarily opening the setting circuit of the switches, as this would result in a failure of the ringing equipment in a reverting call. I

This object is accomplished by providing a differential relay with one winding connected in each leg of. the simplex operating circuit together with means in thecentralized operating exchange for 'unbalancing-the simplex circuit to switch theconnection through by operating the diilerential relay at the correct time i A further object of the invention is to produce suitable arrangements whereby the release of the connection in the remote ex change is left under the control of the calling subscriber until an idle sender has been actually selected in the centralized operating exchange and for then temporarily removing the control of the release from the calling subscriber and for holding the connection in a locked condition until the desired number has been set up and the sender hascompleted its sending operation. This latter object is accomplished by means of a counting device under the control of the above-mentioned dif f-erential relay and in connection with suitable cooperating circuit arrangements in the centralized exchange.

A further-object of the invention is the provision of practical and economical circuit arrangements for putting a system of the foregoing character into successful opera-. tion.

Other objects and features of the invention will appear as the description which is to follow is perused.

ammz description Referring now to the drawing comprising Figs. 1-5, they show by means of the usual circuit diagrams, a suiiicient amount of apparatus in a telephone system embodying the features of the invention to enable the same to be understood.

Referring now particularly to Fig. 1, this drawing shows equipment located in a remotely controlled semi-automatic exchange, connected with the control point by the single operating trunk shown in the lower right h and corner of the drawing. The equipment shown includes the line of substation T1, which terminates at the exchange in the automatic line switch LS1, which has access to selectors among which is selector switch S1. The trunkcircuit TCl is associated with the trunk line leading to selector S1, and it is through this trunk circuit that the trunk finder TF, in which the operating trunk terminates', is associated with the trunk line to enable the automatic switches to be controlled to set up connections.

Referring now particularly to Fig. 2, this drawing shows apparatus located in a semiautomatic exchange which is the control point from which several outlying remotelycontrolled semi-automatic exchanges, such as the one shown in Fig. 1, may be controlled. The equipment shown in Fig. 2 includes aline of sub-station T2, which terminates at theexchange in the line switch LS2, having access to first selectors, one of which is the selector S2. The trunk circuit T02 with which the sender Selector SS1 is associated is inserted in the trunk line between the bank of the line switches and selector S2 for the purpose of enabling an association to be made between the trunk line and an idle sender so that the operator can control the automatic switches to set up desired connections. The operating trunk incoming from the remote exchange shown in Fig. 1 terminates in the lower left hand corner of Fig. 2 in the repeating coil and associated relays which cooperate with the sender selector SS2 to associate the operating trunk with an idle sender when a call arrives over the operating trunk.

The apparatus shown in Figs. 3, 4 and 5, includes the operators sender-controlkey set and associated relays, shown in Fig. 3, and one of the four senders shown in the remaining portion of Fig. 3 and in Figs. 4 and 5. The portion of the sender shown in Fig. 3 includes the relays 311-314, while the registering portion is shown in Fig. 4 and the sending portion is shown in Fig. 5. The layout of apparatus is such that each semi-automatic operator is provided with tour senders, the sender selectors, Fig. 2, which are usually 25-position mechanisms, have access to senders of several operators.

Detailed description The apparatus having been described generally in this manner, a detailed description of its operation will now be given. For this purpose it will be assumed the subscriber at sub-station T2, Fig. 2,'desires a connection to be set up from his line to the line of another local subscriber whose number is, for example, 5326.

Gonnection set up in centralized exchange When the receiver is removed at station T2, the line switch LS2, the circuit of which are not shown, operates in the usual manner to select an idle'trunk, which trunk, it will be assumed, is the one comprising conductors 214- 216. lVhen this trunk is seized,line relay 201 thereof operates over the calling line and at its upper armature places ground on the release trunk conductor 215 so as to guard the trunk line from intrusion and to maintain the line switch LS2 operat d. At its inner lower armature, relay 201 closes a circuit for switching relay 203 in series with the associated operating magnet of the senderselector SS1. At the same time, relay 201, at its lower armature, connects test wiper 206 to the unction of relay 203 and the operating magnet, with the result that the sender selector searches for an idle trunk in the usual man- Sender selection Assuming that the trunk line comprising conductors 209213 and extending to the sender shown in Figs. 3-5 is the one found to be idle, switching relay 203, which is short circuited as long as a ground potential is encountered by test wiper 206, energizes in series with the associated operating magnet, which magnet does not operate at this time on account of the relatively high resistance of relay 203. At its inner lower armature, relay 203 disconnects test wiper 206 from the junction of the winding of relay 203 and the operating magnet and connects the wiper to ground, thereby placing a guarding and holding potential on conductor 211. At its remaining contacts, relay 203 connects up the remaining wipers on the switch SS1. As a result of impulse wiper 207 being connected up at the middle upper armature of relay 203, the upper winding'of line relay. 221 of the selector S2 is energized over the upper talking conductor and over conductor 213 extending to the sender across Figs. 3 and 4 to ground through contacts of the interrupter I in Fig. 5. Upon operating, relay 221 closes a circuit for release relay 222, which operates to prepare the switch for operation- In the selected sender, relay 311 operates over the grounded release-trunk conductor 211 and through contacts of relay 312 and at its lower armature disconnects the corresponding test conductor from ground and extends it to the #1 connecting relay 308. This is preparatory to enabling the distributor D to stop on a contact associated with the #1 sender and operate the #1 connecting relay so as to connect the #1 sender with the operators equipment. At its upper armature, relay 311 places ground on the associated start operating slow-acting relay 304: through contacts of relays 305308. Relay304 closes a circuit for the associated relay 303, which relay operates and starts the hunting action of the distributor D by connecting test wiper 325 to stepping magnet 324-. throughthe selfinterrupting contacts of the stepping magnet. At its two upper armatures relay 303 disconnects common'conductors 326 and 327 from the operators headset and connects the conductor 327 through the associated; condenser to the differential tone generating relay. Each time relay 302 pulls up and closes a circuit for its upper winding in parallel with its lower winding, it falls back dueto the differential relation between its two windings, thereby generating a tone current which is impressed on conductor 327 through the associated condenser. This tone current ,isnot sent back to the calling line for the time being.

The test wiper 325 of the distributor D encounters a ground potential on the test conping operation ceases due to the absense of a direct ground potential on the test conductor and a circuit is closed for relay 308 through test wiper 325 and the lower armature, operated of relay 311, from battery through stepping magnet 324 and the lower contacts of relay 303. Operating magnet 324 does not operatively energize in series with relay 308* owing to the relatively high resistance of the latter. When relay 308' operates, it connects at certain of its lower armatures the 20 six conductors associated with the operators key set to the corresponding conductors of the sender; it closes a locking circuit for it self at its inner lower armature in multiple .25 with the lower contacts of relay it lights the call lamp associated with the operators key set at its upper armature; connects up the conductors 209 and 210 at its intermediateupper armatures'to the common conductors 326 and 327; and at its upper armaturc it opens the circuit of slow-acting relay 304. During the time required for relay 304 to fall back after its circuitis opened, the tone generated by the differential tone relay 302 is heard by the calling subscriber, who is informed thereby that he may now give the'desired number to the operator. Relay 304 falls back shortly and opens the circuit of relay 303 in addition to stopping 1 the generating of tone current, whereupon relay 303 falls back and connects conductors 326 and 327 to the operatorshead-set. At

the time this connection is made, the operciated talking condenser is equalized with thepotential diii'erence across conductors 326 and 327 so as to shield the operator from disagreeable noises in her head-set. Relay 301 falls back an instant later and places the operator into communication with the calling subscriber.

Registration of desired number Upon hearing the number desired by the calling subscriber, which number, as hereinbefore assumed is 5326, the operator depressed the digit keys of her key set forthe respective digits of the number. It will be noted that the four conductors associated with the digit keys are labeled A, B, C, and D. The operation of a given, key results, in the grounding of one or more of these conductors. As an aid in reading the drawing, the conductors grounded responsive to the operation of each key have beeii. noted in parenthesis above each key.

*Vhen the operator depresses the #5 key to set up the first digitb, the B and D conductors are grounded, operating relays Bland D1 of the thousands register Fig. 4, relay 412 being operated at this time from the grounded release trunk conductor 211 through contact of release relay 314 and the inner upper con tacts of the transfer relay 411. Upon 0p-- crating, relays B1 and D1 lock themselves to conductor 323 through transfer relay 411, but relay 411 does not operate until the initial circuit of these relays is opened, being short circuited until this happens.

When the key is released, relay 411 operates in series with relays B1 and D1 (which latter relays remain operated) and at its inner upper armature it disconnects the connecting relay 412, whereupon relays A1D1 are disconnected from the conductors A.-D. At its upper armature, relay 411 places ground on conductor 322 through contacts of relay 414, operating relay313, Fig. 3 to open a point in the switch through circuit to be hereinafter described and to place a multiple ground connection on release-trunk conductor 211. At its middle upper armature, relay 411 extends a ground potential to the relays of the hundreds register, operating relay 422 to connect the conductors A, B, C, and D, to the relays A2, B2, C2, and D2, respectively. Now, When'the operator depresses the #3 key to register the hundreds digit 3, conduc tors A. and D are grounded,operating relays A2 and D2. These relays lock up in series with relay 423, which remains short circuited as long as the key is depressed and operates as soon as the key is released. Relay 423. in

addition to extending a ground potential to the tens register to cause relay 432 to operate, disconnects relay 422 and places a further multiple ground connection on conductor 322.

When the tens digit 2 is registered by depression of the #2 key, relays A3 and C3 are operated over conductors A and C, whereupon they lock up in series with relay 431, which relay operates when the key is released and transfers the control'to the units register 'by releasing relay432 and operating Retransmissrion of number Having. finished setting up the number, the operator depresses the start key, whereupon start relay 312 is operated through conpendulum swings to the left.

tacts of relay 308 and through the lower winding of relay 311 and closes a locking circuit for itself to conductor 211 at its inner upper armature, at'the same time disconnecting the upper winding of relay 311. Relay 311 remains operated through its lower winding until the start key is released where upon it falls back and opens the circuit of relay 308, at the same time replacing ground on the associated contacts in the bank of wiper 325 of the distributor D. Relay 308 falls back and disconnects wiper 325 from the associated operating magnet, at the same time severing all connection between the operators common equipment and the sender #1 and closing the associated point in the chain circuit of start relay 304 so as to enable the distributor D to operate again to connect the operators head-set to another sender which may have been taken for use in the meantime.

As a further result of the operation of start relay 312, it prepares the switchthrough circuit, to be hereinafter described,

at its upper armature, and at its middle armature it places ground from the inner contacts of relay 313 on start conductor 321 so as to start the stepping action of the counting switch CS, Fig. 5, under the control of the marginal stepping relay 501 associated with the interrupter I. 7

It may be pointed out at this time that the interrupter I is first started into operation upon the seizure of the sender when the ground potential is placed on release-trunk conductor 211. This results in a closure of a circuit through the magnet winding of the interrupter I and through the'marginal stepping relay 501 in series. Relay 501 does not operate in series with the magnet winding of the interrupter I, but upon the energization of this magnet windin the weighted pendulum is drawn over to the right, short circuiting the magnet winding of the interrupter whereupon the interrupter magnet deenergizes and thestepping relay 501 energizes. When the pendulum swings to the left it a ain includes the ina met windin 'v of the interrupter in circuit, whereupon relay 501 falls back. As the interrupter I continues to operate, the impulse relay 501 is operated each time the pendulum swings to the right, and the interrupter contacts of the interrupter I are opened each time the Now, the operation of the interrupter I is ineffective, and the operation of'stepping relay 501 is ineffective likewise until start conductor 321 is grounded as above described upon the depression of the start key by the operator, from which time eachdeenergization of stepping relay 501 results in an energization of the operating magnet of the counting switch CS from conductor 321 through contacts of stop relay 503. The

wipers 504 and 505 on the counting switch OS are advanced only upon the back stroke of the operating magnet, and they consequently remain in the position shown upon the first energization of the magnet. When the pendulum of the interrupter I swings to the right and opens the operating-magnet circuit by energizing stepping relay 501, the operating magnet falls back and advances the wipers 504: and 505 one step, whereupon pick-up wiper 504 encounters a'grounded contact, closing a circuit for pick-up relay 502. Pick-up relay 502 operates and prepares a locking circuit for stop relay 503 at its lower armature; places a further multiple ground connection on conductor 322 at its upper armature; and at its inner upper armature it removes one ground connection from the outgoing impulse conductor 213, leaving the conductor grounded only through the contacts of the interrupter I.

Now, with the circuit in this condition, each time the pendulum of the interrupter I swings to the left, it sends an impulse by removing ground from conductor 213 to de-energize the line relay of the selector S1, Fig. 1. The operating magnetis reoperated by the deenergization of stepping relay 501 so that each time the pendulum swings to the right relay 501 reoperates and drops back the operating magnet to advance wipers 504: and 505 another step.

When the wipers ofthe counting switch are advanced again at the end of the transmission of the impulse, wiper 505 encoun ters the bank contact in which the first stop conductor terminates, which stop conductor is grounded only in case the digit being transmitted is the digit 1. The digit being transmitted in this case is the digit 5, stored on the thousands register Th, Fig. 4, from which it follows that the #5 conductor is grounded instead. of the #1 conductor.

The #5 conductor is grounded at this time through the lower armature, normal, of transfer relay 414:, Fig. 4, right hand armature, normal, of relay A1, outer armature, operated, of relay B1, middle armature, normal, of relay C1, and the associated armature, operated, of relay D1. That being the case, the sending operation continues and the advance of the counting switch CS continues until five impulses have been sent by the interrupter I over the outgoing control circuit. At the end of the fifth impulse wiparmature; places a further multiple "ground connection on conductor 322 at still another armature; and at its u per-most armature it disconnects the operating magnet from the impulse circuit controlled by stepping relay 501. v I

1 Responsive to the closure of the restoring circuit of the counting switch GS at the inner upper contacts of relay 503, the selfinterrupting operating magnet operates rapidly in a buzzer-like manner and the wipers 504 and 505 are advanced until they stand in the position shown in the drawing, whereupon the action ceases due to the fact that thenormal Contact in the bank of wiper 504 is ungrounded. At this time the circuit of slow-acting pick-up relay 502 is opened, with the'result't hat the relay falls back shortly and opens the locking circuit of relay 503, which relay shortly falls back to start the transmission of the hundreds digit 3.

When the circuit of stop relay 503 is first closed at the end of the transmission of the thousands digit, a parallel circuit is closed over conductor 401 and through contacts of relay 414 for relay'413. Relay 413 operates locks itself to conductor 323 in series with relay 414, which latter relay remains short circuited until the locking circuit of re lay -3 is opened by relay 502, whereupon relays 414 energizes in series with relay 413 and transfers conductor 401 to relay 423 of the hundreds register.

The sending operatlon proceeds for the second digit in the same manner as described inconn'ection with the first digit and is teri'ninated at the end of the transmission of the third impulse upon the energization of stop relay 5'03, when wiper 505 encounters the hank contact in which stop conductor 3 terminates. The stop conductor #3 is grounded at this time through contacts of relays 414 and 424 and through contacts of the operated relays A2 and D2, in addition to the contacts ofthe unoperated relays B2and C2.

Belay 423 is energized at this time in multiple with the stop relay and locks'itself in series with relay 424, which latter relay opcrates, when the circuit of the stop relay is opened and transfers conductor 401 to relay 433 of the tens register. The stopping ground potential is shifted at the lower contact of relay 424 to the register relays of the tens register.

W hen the retransmission of'the tens digit takes place, the operation is the same as described hereinbef-ore until stop relay 503 operat es at the end of the second interruption in the outgoing control circuit when wiper 505 encounters the bank contact in which stop conductor #2 terminates, stop conductor #2 being grounded at this time through contact of the operated relays A3 and C3 and contacts 011116 non-operated relay B3. Re-

lays 433 and 434 are operated in a manner similar to relays 4 23 and 424- to transfer the control'to'ithe unit register.

Thetransm-ission of the units-digit 6 next takes place and is-ter'minatecl upon the energization of stop relay 503 at the end of the 6th interruption in'the outgoing control circuit when wiper 505 lands upon the bank contact in which stop conductorb terminates,

stop conductor 6 being grounded at this time through contacts of. the non-operated relays A4 and B4 and contacts of theoperated relays C4 and D4. 1 Freeing the s-e'adw it will be noted that each of the relays 414,, 424, 434, and 444., upon operating remoyes ground at one point from the multiplygroundedconductor 322. Now, when relay 444 operates upon theopening ofthe circuit of stow-acting stop relay 503, when pick-up relay 502 falls back at the end of theunit digits, it leaves conductor 322' grounded only at the contacts of stop relay 503. Now, when relay 503 falls back at this time conductor is ungrounded at all points and relay 3l-3, Fig. 3, falls back as a result. Belay 313r1emoves ground from start conductor, 321 at its inner armatureand at its upper armature it removes ground at one point from conduc tOI 211 and Closes the switch-through circuit through contacts of the operated relay 312 and over conductor 212. This circuit includes wiper 205 of the sender selector SS1, Fig. 2, the inner upper contacts of switching relay 203, and the switch-through relay202. Relay 202 operates'and locks itself to releasetrunk conductor 215 at itsinner upper contacts, and at its upper and lower armatures it disconnects the incoming conductors 214 and 216 from the line relay 201 and extends them to the corresponding conductors of the connection established through the selector S2. Asa result. of this, line relay 201 falls back, followed by the fallingback of relay 203 to disconnect the wipers of the sender selector SS1, to free the sender. The established connection is now held up over the line of sub-station C2.

' Whe'nthe sender is freed, the removal of the ground potential from conductor 2111 re: sults in the de-energization of relay 312, Fig. 3, and in the deenergization of relays 411-, 413, and 414, Fig. 4. As a result of'the deenerization of relay 411, relays 421, 423, and 424 fall back and the "deenergization of relays 431, 433, and 434 follows, from which follows thede-energization of relays 441, 443, and 444. The operation of the interrupter I ceases as a result of the removal of the ground potential from conductor 211. Y

The sender is now at normal and may be seized again for use another call.

Setting the switches The response of the automaticswitching mechanism to the impulse trains retransmitted by the sender will now be considered. Returning now to'the point at which the first series of impulses (interruptions) is trans: mitted to the upper winding of line relay 221 of the selector S2, each time the circuit of this upper winding is opened at the contacts of the interrupter I, Fig. 5, line relay 221 falls back and closes a circuit for the associated vertical magnet through the lower armature, operated, of relay 222 and the winding of series relay 223. By the operation of the vertical magnet the wipers 226228 are raised step by step until they come to rest opposite the fifth level of bank contacts, the digit received being-the digit 5. Relay 223 energizes in series with the vertical magnet when the first impulse'is received, and, being slow acting remains operated throughout the series of impulses, Upon operating, relay 223 prepares a circuit from the grounded release trunk conductor 215 for relay 224, which is closed as soon as the associated off-normal contacts have closed upon the first vertical step. Upon operating, relay 224 prepares .a circuit for themtary magnet at its lower armature and its upper armature closes a locking circuit for itself from theinner lower contacts of relay 228 and including the associated rotary-magnet interrupter'contacts and the associated off-normal contacts.

At the end of the vertical movement, relay 223 falls back and closes the rotary magnet circuit, whereupon the rotary magnet operates and advances the wipers 226228 one step. If the trunk line terminating in the first set of bank contacts is idle, switching relay 225 operates inseries with relay 22 1 and seizes the trunk. Assuming, however, that trunk line is busy, relay 225 is short circuited by the ground potential encountered on the test contact by test wiper 227 and does not operate. Relay 224; operates again through test wiper 227, and the rotary magnet is reoperated to advance the wipers another step.

This alternate operationof stepping relay 22 1 and the associated rotary magnet con-' tinues until an idle trunk line is reached,

relay 128.

slow acting" release relay 222 falls back a m0+ ment later. I 1 Responsive to the transmission of the remaining digits, the remaining portion of the connection to the called line is set up in the well-known manner.

The established connection is held over the calling line and over the two local talking conductors in series after the connection has been switched through upon the operation of the switch through relay 202 of the trunk circuit TC2;

'ReZease of connection I The conversation between the called subscriber and the calling subscriber takes place in the usual manner when the called subscriber responds, and the connection releases in the well-known manner when the subscriber at substation C2 replaces his receiver. The release of the switches LS2 and S2, as well as the trunk circuit T62, it may be pointed out, takes place when the ground potential is removed from the release trunk conductor of the established connection by the final switch. When this occurs, switching relay 225 of the selector S2 and switchthrough relay 202 of the trunk circuit T02 both tall back. The switching relay 225 closes the circuit of the associated release magnet at its inner lower contacts, through the lower contacts ofrelays 221 and 222 and through the associated oft-normal contacts. By the operation of the release magnet the mechanism of the switch is restored to its normal position, whereupon the oil-normal contacts associated with the release magnet open the circuit thereof.

It will now be assumed that the subscriber at substation T1, Fig. 1, desires to converse with another subscriber whose lines terminates in the same remote exchange and whose number is, for example, 914.

Connection set up in remote ewchcmge When the receiver is removed at substation T1, the line switch LS1 operates in the usual manner to select an idle trunk, the trunk comprising conductors 112114:, for example. When this trunk is seized, line relay 102 ene'r gizes over the calling line and places ground on the first-level start conductor 119 at its upper armature. t its lower contacts relay 102 removes the guarding potential from the associated test contact in the bank of the trunk finder TF and prepares a holding circuit for l/Vhen the first-level start conductor 1 19 is grounded as above pointed out, a circuit is established through the associated resistance and over conductor 120 for startrelay 129 through contacts of relay 127 and contacts of the release magnet. Start relay 129 operates and closes at its second armature from the bottom a circuit through the contacts of the vertical magnet','contactsoi relay 131, con tacts of the rotary magnet and its own lower contacts tor stepping relay 130. Relay 130 operates and completes a circuit for the vertical magnet at its lower contacts, whereupon the vertical magnet responds by raising the wipers121136 and the test wiper 136 one step. The vertical magnet also opens the initial circuit of stepping relay 130. In case there is no call waitin on the first level, this results in a deenergization of stepping relay 130 and in a further operation of the vertical magnet. In this case, however, the calling trunk is reached from the first level of the finder and test wiper 136 encounters a ground potential on the first level-test contact over the start conductor 119 with the result that relay 130 remains operated notwithstanding the opening of" the vertical magnet interrupter contacts. The new circuit includes normally closed contacts controlled by the inner lower armature of relay 131, the lower winding of relay 131, vertical test wiper 136 on its first level contact, and the grounded start conductor 119. Relay 131 operates in series with relay 130 and closes a locking circuit for its upper winding through its upper contacts at re lays 129 and 128.- Relay 131, at its lower armature, transfers themagnet-operating circuit from the vertical magnet to the rotary magnet; while at its inner lower armature, it closes transfer relay 1301mm the vertical test wiper 136 to rotary test wiper 125. Relay 130 is now held energized in a locking circuit including its own inner lower contacts and the middle lower contacts of relay 129.

When the rotary magnet operates, it advances the wipers1'121-.126 one step into engagement with the first set of contacts in the first level, and it opens the circuit of relay 130. Relay 130 thereupon falls back and opens the circuit of the rotarymagnet and a further point in its own circuit. ther operation depends upon whether the trunk line TCl terminates in the first set of contacts in the level or in some other set. It will be assumed that the latter is the case. iVhen rotary magnet 130 falls back, it closes a circuit for relay 130 at its interrupter contacts through the third armature from'the bottomof relay 131, to ground through test wiper'125 and the grounded test contact on which it is standing. It will be noted that the presence of this ground potential is the i only thing which prevents the lower winding of relay 128 from energizing through the inner lower contact of relay 129 in series with relay 130. Relay 130 reoperates and again closes a locking circuit for itself at its inner lower armature, at the same time again-operating the rotary magnet to bring about a further advance of the wipers of the switch.

This stepping operation of the trunk finder TF continues until the wipers land upon the contacts associated with the trunk circuit The fur TCl, whereupon the action ceases due to the fact that there is no ground potential on the test contact in the bank of Wiper 125 because line relay 102 is operated. In this case, relay h 130 does not operate through the test wiper again and relay 128 energizes in series with relay 130, but relay 130 does not operate again owing to the relatively high resistance of the lower winding of relay 128. When relay 128 operates, it closes a locking circuit for itself at its inner upper contacts and over test w1per 12 4 and the contact 011Wll10l1 it 18 standing and through the lower armature of line relay 102. At its middle armature, relay 126 opens p the circuit of relay131, and at its lower armature it closes a circuit for relay127. Relay 127 operates and at its inner upper armature opens the circuit of start relay 129, whereper armatures and at its lower armature, relay 127 connects up wipers 121123 and 126.

As a further result of its operation, above described, relay 128- at its upper armature upon this relay falls back. At its three upconnects impulse relay 128 to the conductors through contacts of relay 127 and over wiper 123 to the upper winding of line relay 104 of the selector S1 by way of contacts of relay 108. Relay 104 operates, followedby the energization of relay 105 to prepare the selector S1 for operation.

' Differential relay 132 operates, because current is flowing through only one winding, and closes a circuit for the upper winding of twodim "its

step relay 133, which relay operates through v its first step. 7

In the centralized exchange, relay-241, upon operating over the operating trunk as above mentioned, closes at its inner lower and middle lower armatures circuits for causing the sender selector SS2 to advance under the control of test wiper 249 in search of an idle sender in the manner hereinbefore described in connection with the sender selector SS1. When an idle sender is found, the one .for example shown in Figs. 3-5 and reached by way of conductors 209213, switching relay 245 operates, and, in addition to grounding test wiper 249 at itsinner lower armature, connects up'wipers 247, 250, and 251 at its remaining armatures.

Upon referring again to Fig. 1, it will be noted thatthe releaseof the connection es tablished to the idle sender is under the con trol of the subscriber at substation Tl'and that should he hang up his receiver at this tion.

stage before communicating with-the operator, the connection would release responsive to the falling back of line relay 102 of the trunk circuit TCl, which would be followed bythe deenergization of relays 128, 127, and

132134 of the trunk finder TF and the release of the trunk finder. In the sender selector SS2, Fig. 2, relay 245 would fall back as a result of the deenergization of relay 241. This is mentioned at thispoint owing to the fact that this condition will be changed as will be pointed out hereinafter. When wiper 250 is connected up, relay 244 energizes through this wiper from ground on impulse conductor 213, which is grounded through contactsat relay 502 of the sender. Relay 244 looks itself energized and transfers the incoming impulse conductors to wipe 250, at the same time closing a local circuit for relay 241 through resistance 246. Current now flows from the grounded conductor 213 Y and through wiper 250 over both conductors of the operating trunk, whereupon differential relay 134, Fig. 1, falls back and opens the initial circuit of the upper winding of relay 133, whereupon, the lower winding, which has been short circuited heretofore, energizes in series with the upper winding and operates the relay through its second step. At this time, relay 133 at its lower armature, places the associated resistance in shunt of the talking condenser connecting the left-hand repeating coil windings. This establishes a parallel circuit for line relay 102 so as to hold this relay energized independent of the calling party until the connection has been set up.

Responsive to the grounding of release trunk conductor 211 of the sender through test wiper 249, relay 311, Fig. 3, operates as hereinbefore described to cause the opera-' tors equipment to become connected with the selected sender, and the interrupter I, Fig. 5, begins the hereinbefore-described opera- It will be remembered that the energization of relay 311 is followed by the energization of relays 304 and 303 and by the step-by-step operation of the distributor D which results in the distributor D landing upon the contact leading through the lower armature of the operated relay 311 to the #1 connecting relay 308, and that the resulting operation of relay 303 is followed by the deenergization of relays 304 and 303 whereupon the connection is completed from the calling line to the operators telephone after a momentary application of the current has been made to the calling line to inform. the calling subscriber that the operator is waiting for the number. I Y

After learning the desired number from the subscriber, which number as hereinbefore assumed is 914, the operator depresses the #9 key, the #1 key and the #4 key, one after the other, with the result that the digits first digit is stored; that relay 421 operateswhen the second digit is stored; and that relay 431 operates when the third digit is stored. When these three relays are operated, conductor 322 is grounded at three points. 'Relay 313, of course, is operated upon the first application of ground potential to conductor 322 when the digit 9 is stored.

Having set up the three digits in the called number, the operator depresses the start key, Fig. 3, operating relay 312 to start the sender to operate and to disconnect the operator from the sender by releasing relay 311' when the start key is closed. The sending apparatus of Fig. 5 now operates responsive to the ground potential on start conductor 321 and retransmits the stored digits 9, 1, and 4 in the hereinbefore described manner. It

will be remembered that relay 413 of the potential is removed at the last point from conductor 322. Relay 313 falls back and closes the prepared switch-through circuit (through the upper contactsof relay 312 and over conductor 212) for switch-through relay 243, of the sender selector SS2, by way of wiper 248 and contacts of relay 245. Relay 243 operates and locks itself through contacts of relay 241 and it opens the circuit of relay 244 at its inner lower armature, whereupon relay 244 falls back and transfers the upper conductor of the operating trunk back to relay 241 and again opens the lower conductor. When this-occurs, differential relay 134, Fi 1, pulls up again and, this time closes a circuit through contacts at relays 133 and 127, and through wiper 122 for switch-through relay 103.

Relay 103 operates and locks itself to the associated grounded release conductor 113 at its inner upper armature, and at its upper and lower contacts it switches the conductors connection with any subsequent: call.

through contacts of relay 129 and off-normal contacts, The release magnet operates and restores the finder to-its normal position in the usual manner, whereupon the release magnet circuit is opened at the associated odnormal contacts, The contacts of the release magnet maintain start relay 129 discon nected during the releasing operation. It

will be noted that the circuit for maintaining relay 129 disconnected after the finder has operated is taken through contacts of relay 127, .which is a slow acting relay and that the release magnet circuit is closed. at the same timethat the circuit of relay 127 isopened.

Due. to the fact that relay 127 is slow acting the release magnet has time to energize and disconnect relay 129 at a further point before the slow acting relay 127 falls back and closes the associated point in the circuit of relay 129. This is of utility in case the start conductor is grounded at the timethe release occurs, as it prevents the finder from trying to test while it is releasing. Relays 132-134 fall back when relay 12.8 restores. As a result of the opening of he upper contacts of relay 128, line relay 241, Fig. 2,'falls back and opens the circuit of relays 243 and 245,

which relays fall backand restore the associated circuit connec to norm l- The operating trunk may now be used n The connection set up through switch LS1. and the Selector S1 is released in the usual manner when the calling subscriber replaces his receiver after conversation. The release of the selector upon the falling back of relay 108 is brought about by the energization of the release magnet of the selector when ground potential is removedfrom the release trunk conductor of the established connection, and the locked up switch-through relay 103 falls back at the same time.

Referring again to Figs. 3 and 4, it may be pointed out that the operator can release a partial registration by operating the release key shown-in the lower left hand corner. of Fig. 3 in case she discovers that she has made an error. When the rele-ase'key is operated, relay 314 pulls up and disconnects the grounded conductor 211 from conductor 323, permitting the registering apparatus of Fig. 4 to restore to normal. Following this, the operator permits the release key to restore and proceeds to set up the number by operating her numberkeys in the usual manner.

the line In case acall comes into the operator and no response is secured to the-momentary ap plication of tone current and to a challenge by the operator, she may cause the connection to be switched through-to the first selector and therebyfree the sending equipment, by operating her startkey without first setting.

up a number.. As an alternative, the opera tor may set up a predetermined number and cause the call to be trunked to a spec1alpos1- tion especially, equipped for handling false calls. This latter arrangement is usually preferable, it enables the attendant at the special position to make proper record of false calls so that their causefmay be located and remedied.

hat is claimed is: v y, I 1. In a multi-office semi-automatic telephone system, a first ofiice and a second .oflice,

operator-controlled senders located in the first office, and means including local trunks and inter-ofii'ce trunks whereby the said send ers are used to control the operation of the automatic switches to set up connections local to both oflices. 1 v

2. In a telephone system wherein connections areset up through automatic switching,

mechanism controlled from. an operatorsv I switchboard through the intermediary of register senders at such switchboard, operators common equipment, means for seizing sald register senders at random as calls are initiated, and meansit'or automatically connectmg the associated common equlpment with any se1zed sender. 1

3. In a telephone system wherein register senders are provided for controlling automatic switches, an operators switchboard, a plurality of registersenders at said switchboard accessible to calling lines, a distributing device atsaid switchboard having ac.-

cess to each of said senders, and means responsive to the seizure of one of said senders for advancing said distributing device and for bringing it to rest in association with the seized sender. V

4. In a telephone senders are provided for controlling automatic switches, an operatorsswitchboard, a plurality of register senders'at said switchboard accessible to calling lines, a distrib-- uting device at said switchboard having access to each of said senders, means responsive to the seizure of one of said senders for advancing said distributing device and for bringing it to rest in association with the seized sender, operators common eqmpment,

a connecting relay associated wit-h' each of said senders, and'means' controlledfby said distributing device when it finds a seized sender for operating theconnecting relay of such sender'to connect the operators com-:

i switchboard, a common talking circuit com;

system wherein register prising two sections the first of which extends to the operators telephone, a plurality of individual talking circuits terminating at said switchboard, automatic means for extending connections from subscribers lines to any one of said individual talking circuits, means in cluding a hunting device responsive to a connection extended to one of said individual talking circuits, for impressing a tone current on the second section of said common talking circuit and for starting said distributor to connect the seized individual talking circuit with the second section of said common talking circuit, and means effective a moment after the said connection is effected for discontinuing the application of tone current to the said second section of the common talking circuit and for uniting the two sections so that the operator may converse with the calling subscriber.

' 6. In a remotely-controlled semi-automatic exchange system, means responsive to the initiation of a call on a line terminating in a remotely-controlled semi-automatic exchange for extending such line to an automatic'directive switch, an operating trunk extending from theremotely controlled exchange to an operating point, means responsive to the said initiation of a call for associating said operating trunk with the said directive switch and for establishing a switch-control circuit over said operating trunk, means including a sending device at the operatlng point for interrupting the control c1rcu1t over said operating trunk to set up a desired connection through said directive switch,and means controlled from the operating point over the control trunk after the connection has been set up for causing a switch-through operation in the semiautomatic exchange and the freeing of the operating trunk thereat, while maintaining a current flow over the. control circuit until theswitch-through operation has been ef- 'fected.

7. In a remotely-controlled semi-automatic exchange system, means responsive to the initiation of a call'on a line terminating in a remotely controlled semi-automatic exchange for extending such line to an automatic directive switch, a two conductor operating trunk extending from the remotely controlled exchange to an operating point, means responsive to the said initiation of a a call for associating said operating trunk with the said directive switchand for establishing-a switch-control circuit over said operating trunk, means including a sending device at the operating point for interrupting the control circuit over said operating trunk to set up a desired connection through said directive switch, and means controlled from the operating point over said operating trunkto switch the connection through at the semi-automatic exchange and to free the associated end of the operating trunk by unbalancing the current fiow'in the tw conductors of the operating trunk.

' 8. In a remotely-controlled semi-automatic exchange system wherein the switching apparatus in a semi-automatic exchange is controlled over an operating trunk from a contl'ol point, the operating trunk being associated successively with trunk lines over which connections are to be set up, means responsive to the association of the operating trunk with a local trunk when a connection is to be set up thereover for establish-' ing an unbalanced current flow over theopcrating trunk, means at the control point responsive to such unbalanced flow for signalling the operator at the control point.

' 9. In a remotely-controlled semi-automatic exchange system wherein the switching apparatus in a semi-automatic exchange is con trolled over an operating trunk being asso' ciated successively with trunk lines over which connections are to be set up, means responsive to the association of the operating trunk with a local trunk when a connection is to be set up thereover for establishing an unbalanced current flow over the operating trunk, means at the control point responsive to such unbalanced flow for signalling the operator at the control point, and means responsive to the extension of the connection from the control trunk to the operators equipment for balancing the current flow over the operating trunk.

10. In a remotely controlled semi-automatic exchange system wherein the switching apparatus in a semi-automatic exchange is controlled over an operatingtrunk from a controlled point, the operating trunk being associated successively with trunk lines over which connections are to be set up, means responsive to the association of the operating trunk with a local trunk when a connection is to be set up thereover for establishing an unbalanced current flow over the operating trunk, means at the control point responsive to such unbalanced flow forsignalling the operator at the control point, means responsive to the extension of theconnection from the control trunk to the operators equipment for balancing the current flow over the operating trunk, and means responsive thereto for removing the release of the connection from under the control of the calling line.

11. In a remotely controlled semi-auto unbalanced current flow over theoperating trunk, means at the control point responsive to such unbalanced flow for signalling the operator at the control point, means responsive to the extension of the connection from the control trunk to the operators equipment for balancing the current flow over the operating trunk, means responsive thereto for removing the release of the connection from underthe control of the calling line, and means responsive to a further unbalanced con-. dition of the operating trunk after the control has been exercised from the operating point for switching the connection through from the calling line to the set up connection through the automatic switches and for disassociating the operating trunk from the local trunk line.

12. In a semi-automatic telephone system wherein a remotely controlled semi-automatic exchange is controlled over a two-conductor operating trunk extending between that exchange and an operating point, which trunk is associated with calling lines successively in the semi-automatic exchange, means controlled over the two operatingtrunk conductors for setting the switches in the semi-automatic exchange, and means responsive to current flow over one conductor only of the operating trunk for freeing the operating trunk from an established connec tion.

13. In a semi-automatic telephone system wherein a remotely controlled semi-automatic exchange is controlled over a two-conductor operating trunk extending between that exchange and an operating point, which trunk is associated with the calling lines successively in the semi-automatic exchange,

means controlled over the two operatingtrunk conductors for setting the switches in the semi-automatic exchange, means for stopping the current flow over one conductor of the operating trunk while permitting the current flow over the other conductor thereof, and means responsive theretofor freeing the operating trunk from the established connection and for switching such connection through and placing it under the control of the calling line.

14. In a multi-ofiice automatic telephone system, a group of register senders located in a first oifice, operators setting equipment common to said register senders, means responsive to current flow over one conductor ing line local to said first oifice or on a calling line local to a second oflice for associating an idle one of said register senders with the calling line, and means for thereupon associating the operators common setting equipment with the last named register sender.

15. In a multi-oflice semi-automatic telephone system, a first ofiice and a second office, automatic switches in each office arranged to extend calling lines directively, register senders in the second oflice arranged to exercise directive control over said automatic switches, a trunk line connecting said otfices, means responsive to a call on a line in the second oifice for extending a connection to one of said automatic switches and for ex-v tending a branch connection directly to an idle one of said register senders, and means responsive to a call on a line in the first office for extending a connectionto one of said an: tomatic switches and for extending a branch connection by way of said inter-ofiice trunk line to an idle one of said register senders.

16. In a multirofi'ice semiautomatic telephone system, a first oifice and a secondofiice, automatic switches in each oifice arranged to extend calling lines directively, trunk lines in the second 'oflice extending to an operators switchboard, an interoflicetrunk line extending from the first oflice to the second oifice, means responsive to a call on a line in the second oifice for extending a connection to One of said automatic switches in the second I operator for operating the automatic switch one of said automatic switches inthe second officeand for extending a branch connection directly to an idle one of said trunk lines leading to the operators switchboard, means responsive to a callo'n theline in the first oifice for extending a connection to one of said automaticswitches in the first oifice and for extending a branch connection by way of said interoffice'trunk line to an idle one of said trunk lines leading to the operators switchboard, and means for enabling the operator at said switchboard'to converse with the subscriber on either of said calling lines over the branch connection and for operating the automatic switchto which the calling'line is connected. I i

18. In a telephone system, an operators switchboard, a plurality of trunk lines at said operators switchboard, talking conductors at said switchboard individual to the operators headset and common to said trunk lines, means for extending connections from calling subscribers lines to idle ones of said trunk lines, means for connecting the said headset conductors to any one of said trunk lines, and means for thereupon making a momentary'application of tone current to the said headset conductors to inform the cal ing subscriber on the calling line that he is in communication with the operator.

19. In a semi-automatic telephone system, trunk lines over which telephone connections are set up through the medium of automatic switches, register senders for controlling the automatic switches to set up the said telephone connections link circuits arranged to interconnect said trunk lines and said register senders, operators equipment common to said link circuits and including a group of digit keys and a start key, means for setting up a connection between one of said trunk lines and one of said register senders by Way of one of said link circuits, means for setting up a connection from the operators common equipment to the last named link circuit and register sender, said last means including a distributing device having access to each of said register senders, registering means in the connected register sender responsive to successive manipulations of the operators digit keys for registering the digits of a desired number, means responsive to an opera tion of the operators start key for starting the register sender to retransmit digits by Way of the connected trunkline to cause the desired connection to be set up by way of automatic switches, and means in the connected link circuit responsive to the release of said start key following its operation for advancing said distributing device to dis associate the operators common equipment from the link circuit and connected register sender.

20. In a semi-automatic telephone system, trunk lines over which telephone connections are to be set up through the medium of automatic switches, register senders for controlling said automatic switches, operators common equipment for controlling said register sendersincluding digit keys and the start key, a distributing device associated with the operators common-equipment and having access to all of said register senders, means responsive to a calling condition on any one of said trunk lines for connecting any idle one of said register senders to such trunk line and for operating said distributing device to connect the operators common equipment to the connected register sender, registering means in the connected register sender responsive to actuations of the operators digit keys to store digits of a desired telephone number, and means. responsive to an operation of said start key for starting the register sender to transmit the stored digits to the automatic switches by Way of said

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