US1729858A - Telephone system - Google Patents

Description

Oct. 1929. L, RUGGLES 1,729,858

TELEPHONE SYSTEM Filed'Aug. 13, 1926 7 Sheets-Skleeo` 1 Oct. l, 1929. l.. L. RUGGLES 1,729,858

TELEPHQNE sYsTu Filed Aug. 1s, 192e 7 sheets-sheet 2 STATION SELECTOR CONNECTOR l.. 1. RUGGLES 4 '151111151101111 SYSTEM Filed Aug; 1:5. 1926 '7 Sheets-Sheet 5 A j j. N 1 w .H L. .F1 A. u Hu s@ :Him z LWI. T., QN m .Tm ,WV

Oct. l, 1929. L. RUGGLEs TELEPHONE SYSTElf Filed Aug. 13, 1926 7 Sheets-Sheet 4 Ell l l ZES @5U- Filed Aug. 1s, 1926 7 Sheets-Sheet 5 Leuna @7^ PdLHuiqles lL. L. RUGGLES TELEPHONE VSYSTEM oct. 1, 1929.

7 Sheets-Sheet 6 Filed Aug. 13, 1926 Im Lennard L .Bgles Oct. 1, 1929. L l. RUGGLES TELEPHONE SYSTJII med Aug. 1s, `192e -7 Sheets-Sheet 7 Zes QM WN NM Nm Patented Oct. `l, 1929 UNITED sTATEs PATENT OFFICE LEONARD L. RUGGLES, 0F WHEATON, ILLINOIS, ASSIGNOR- TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE TELEPHONE SYSTEM Application led August 13, 1926. Serial No. 128,937.

The present invention relates to telephone systems in general, but is more concerned with party line telephone systems. One object of the invention is the production of new and improved arrangements whereby' reverting calls may be made in a party-line telephone system in which directors are eniployed.

Another object is the production of a new and improved arrangement whereby all positions of the station selector used at a party line connector may be iitilized when ringing current is connected to alternate contacts in the bank of any one Wiper to prevent injurious sparking and short circuiting of the ringing leads as the wiper i.smoved over its contacts.

Considering now the reverting call arrangement, as is well known, arrangements are provided in the so-called ring-back switches so that when the calling subscriber hangs up, after having set a ring-back switch in such a position that the calling and called party-line stations on the calling line will be signalled alternately. the ring-back switch is locked in its operated position and -it holds the previously operated switches until either the calling orthe called subscriber removes his receiver, whereupon the locked-up condition is `terminated and the ringing current is removed'. In case the calling subscriber hangs up before the ring-back switch has been operate-d, the connection is released 11i the usual manner, as the locking arrangement does not become efective until after the ring-back switch has been set. Now, when the director system (a register sender system) is applied to a party line telephone system employing ring-back switches, the two systems will not work together unchanged in case the calling subscriber hangs up promptly after dialling the special number required to set the ringback switch in the desired position, as the director must be allowed a slight time interval to finish sending after the last digit has been registered. Three different arrangements have been evolved for handling thesituation. The simplest of, .these arrangements is the one in which the subscribers are instructed to wait after dialling until) a sotor which will switch through and free itself immediately upon the dialling of a special ring-hack prefix. Following the dialling of this prefix, the calling subscriber dials sufficient digits to trunk the call to the ring-back switch and to set the same in the desired position. This arrangement necessitates that .the subscriber dial more digits than may be required otherwise, but, on the other hand, he is not compelled tone before he hangs up.

The third arrangement developed is slightly more complicated than either ofthe other two, but is thought to be the best from an operating standpoint. According to the third arrangement, the calling subscriber dials two digits indicative of a ring-back connection, followed by the two digits necessary to set the ring-back switch. When the last digit of the number has been dialled, the connection is locked up by the director. This locked conditionis maintained by the director v,until it has finished setting the ring-back switch, whereupon the rangedto permit the Idirector to bring about the switch-through operation in the trunk circuit with the line and release relays of the trunk circuit deenergized, as the switchthrough circuit is normally complet-ed through working contacts of the line relay.

In addition to the foregoing, arrangements have been provided in the director which are applicable to director systems of general usefor keeping a record of the manner in which v the calls are handled. A record is made of the total number of times that the director is seized; a record is made of the total number of times that the director switches through; a record is made of the number of times the director switches through because no dialling takes place after the director is seized or when the delay between successive digits is longer than is permitted; and a record is made of the total number of times that the director switches through when the call is successful as far as the director is concerned.

Other objects and features having to do for the most part with the circuit details involved in carrying out the foregoing will appear upon a perusal of the detailed description which is to follow:

Referring now to the accompanying draw ings comprising Figs. 1-8, Figs. 1-7 are circuit diagrams showing a sufficient amount of eqiupment in a system embodying the features of the invention to enable the invention to be understood, and Fig. 8 is a layout drawing showing how the various sheets of drawings should be assembled together` in order for them to be understood best.

Referring now to Fig. 1, this drawing shows by means of dotted rectangles the oiiice selector OS, the thousands selector M, and the hundreds selector C. This drawing shows also the trunk circuit TC inserted in the trunk line extending from the line- 'switch bank terminals 2-4 to thek office selector OS. The director selector DS is shown associated with the trunkl circuit TC for the purpose of connecting up an idle director to handle the call when the oilice selector OS is seized.

Fig. 2 shows a party-line connector having access to ten-party lines, one of which is shown in the drawings. The station selector individual to the connector is shown to the right of the connector. This station selector is operated in the usual manner after the connector has been set on the called line to select the particular called station that is to be s' alled.

ig. 3 shows a so-called ring-back switch which is used when the calling subscriber desires to converse with another subscriber on the same line to operate the ringers at the two substations alternately.

One of the directors accessible to the director selector DS, Fig. 1, is shown in Figs. 4-7. The portion of the director shown in Fig. 4 comprises the input control switch IOS and the output control switch OCS, together with the relays 301 and 302 that control the stepping of the input control switch.

The portion of the director shown in Fig. 5 includes the sending switch SS, the registers or meters 407-410, and the relays 402-406 which have various controlli-ng functions, as will hereinafter appear.

The portion of the director shown in Fig. 7 includes theoiiice register OR that records the two office digits in the regular subscribers numbers, andthe intermediate distributing frame I.D.F. This drawing shows` also the special relay ,506 that is operated when a reverting call is made so as to` adapt the director for holding the connection after calling subscriber has hung up and until the ring-back switch has been operated.

The portion of the director shown in Fig. 7 includes the thousands, hundreds, tens, and units registers.

@all to Substatioa 100 It will now be assumed that a calling subscriber, desiring to converse with the subscriber at substation 100, Fig. 2, removes his receiver, and that his individual line switch seizes the trunk line comprising conductors 5-7 at the terminals 2 4. When this occurs, line relay l2l energizes over the calling line andat armature 24 closes a circuit for release 22. Release relay 22 responds and at armature 20 places a ground potential on release trunk conductor 6 so as to maintain the calling line switch operated. At armature 28, relay 22 closes a circuit through relay 32 and stepping magnet 33 of the irector selector DS in series, at the same timev connecting test wiper 41, at armature 27, to the junction of the said relay and magnet. In case the trunk line upon which the wipers of the director selector DS is standing is idle, relay 32'energizes regardless of the connection made to the test wiper, leaving the trunk line and the'director through which it extends. Assuming that this director is busy, a ground potential is encountered on the busy test contact lby test wiper 41 and relay 32 is 'short circuited and does not energize. As a result of this same ground potential, stepping magnct 33 operates in its usual buzzer-like manner to advance the wipers step-by-step in search of an idle director. Assuming that the director reached through conductors 43--46 is the first one found to be idle, the wipers 39-42 come to rest on the bank contacts to which these conductors are connected, and relay 32, being no longer short circuited, now energizes in series with stepping magnet 33. At armature 36, relay 32 disconnects test wiper 4l from the test circuit and connects it to ground through the working contact and armature 28, making the seized director busy. At armature 3 relay 32 prepares the combined impulse and switching circuit, and at armatures 34 and 35 it connects the conductors 5. and 7 leading to oiiice selector OS to the corresponding conductors 43 and 44 of the seized director. Responsive to this latter operation of the lin'e relay of the oiiice selector OS energizes over conductors 43 and 44 and the selector is prepared for operation in the usual manner. Polarized relay 452, Fig. 5, is inthev eluded in the circuit of the line relayof the selector OS, but relay 452 -is not operated at this time owing to the way in which it is polarized. l

In the seized director, release relay 404, Fig. 5, energizes lover lconductor 45 "and through the resting contact and armature 415 responsive to the grounding of vconductor at armature 36 of relay 32, 4Fig. 1. At armature 417, relay 404 removes ground from restoring conductor 304, and at armature 418 it removes ground from the release conductor 430.

The calling subscriber may now proceed to call the various digits in the desired number.

. To do this, he first dials two di its indicating the office in which the desired l1ne terminates, and then follows with four digits indicative of the line, and a stations digit to indicate the station on the line, as the substation 100 is a party-line substation. It has been assumed that the bank contacts 501, Fig. 6, are the ones assigned to the local office. Accordingly the di its dialled are those necessary to bring the wlpersv 523 of the ofce register into engagement with the bank contacts 501.

When the first digit is dialled, line relay 21, Fig. l, falls back a number of times correspondin to the number of interruptions produced 1n its circuit at the calling substation. Each time it falls back, it closes at armature 25 a circuit through the working Contact and armature v26, armature 37 and its working contact, Wiper 42 and thebank contact on which it is standing, conductor 46, armature 414, Fig. 5, and its resting contact, conductor 303, series' relay 301, Fig. 4,'lower wiper of the input control switch ICS and its first bank contact, the corresponding conductor, and vertical magnet 504 of the oflice register OR to battery. By its operation,

lce

vertical magnet 504 raises the wipers 523 stepby-step until they come to rest opposite the desired level of bank contacts. Relay 301, Fig. 4, o crates in series with the vertical ma et w en the first impulse is transmitted, am?? being slow. acting, remains operated throughout the series of impulses, A t its upper armature, relay 301 closes a circuit for relay 302, and relay 302 operates and prepares a circuit for the operating magnet of the input control switch, `which circuit is momentarily closed at the end of the series of impulses when relay 301 falls back and pending the falling back of the yslow acting relay 302. When the operating magnet of the input control switch is momentarily energized, the wipers of this switch are advanced one step; and the impulse conductor is shifted from the vertical magnet of the oitice register to the rotary magnet 505.

lrVhen' the second digit is dialled, the impulses of current are transmitted over the' point the impulses are delivered to the rolICS a starting circuitlto e hereinafter referred to is closed.

When the thousands digit is dialled, the thousands register, Fig. 7, is set to register the digit; the hundreds re ister registers the hundreds digit when it is dialled; the tens and units registers register the tens and units digits, respectively; and the stations register registers the digit dialled to indicate the particular station desired on the party line., the input control switch ICS being advanced one stepy at ythe end of each digit.

Returning now to the point at which the input control switch advances into its third position at the end of the setting of the oice register, the upper wiper of the input control switch connects ground to the lower wiper of the switch ICS and through the associated interrupter to conductor 305, whereupon impulses are delivered over conductor 305 and through the resting contact and armature 423 to the stepping magnet 427 of the sending switch SS. Upon the first deenergization of magnet 427, its backacting armature advances the wipers 428 and 429 by means of the usual pawl-and-ratchet arrangement one step, and wiper 428 encounters a grounded bank contact, closing a circuit for pick-up relay 405. At armature 420, relay 405 grounds release trunk conductor 45 at a second point so as to prevent the release of the director While the sending switch SS is oil.

normal; it removes at armature 419 a shunt from around sending contacts 425; and at armature 421 it closes a circuit through armature 424 and its resting contact, and including conductorv 309, for back-acting magnet of the output-control switch OCS, Fig.

4. As a result of the removal of the shunt at armature 419 from around the sending contacts 420, each subsequent energization of magnet 427'results in an 'opening' of the bridge across the conductors 43 and 44, the wipers 428 and 429-being advanced one step at the end of each interruption of the current flow. At the end of the first interruption, wiper 429 encounters the first impulse stop conductor and it is advanced over the successive stop conductors as the other interruptionsA arey produced and terminated.' Since the single office digit necessary in the present case to operate the oilice selector OS the third interruption in the outgoing control circuit, a circuit is closed for stop relay 406, Fig. 8. Relay 406 energizes and places a shunt at armature 422 around the sending contacts 426; opens the interrupter circuit of magnet 427 at armature 423 and closes a local restoring circuit through self interrupting contacts 425; and at armature 424 it removes ground rom conductor 309 and closes a self-locking circuit. As ground is now removed rom conductor 309, the stepping magnet of the switch OCS falls back and advances the associated wipers one step. As only one office digit is needed, the remainin" bank contacts in the group 501 of the oce register OR, Fig. 6, are cross connected to thc skip conductor 310, .and a circuit is closed over conductor 310 and through the self-interrupting contacts of thc switch OCS for its stepping magnet, automatically advancing the wipers of the switch OCS through the second, third and fourth positions. The advance of the switch ceases when the lower wiper lands 0n its fifth bank contact.

As a result of the closure of the local restoring circuit for the stepping magnet 427 of the sending switch SS, this stepping magnet operates through the self interrupting contacts 425 and through the restoring wiper 428 and restores the switch SS to its normal position, opening the circuit of the slow acting pick up relay 405. Pick-up relay 405 falls back after a short interval and opens the locking circuit of relay 406 at armature 421. Relay 406 falls back at the end of a further interval and starts the sending switch SS to transmit the thousands digit of the number, unless the thousands register is still in its normal, in which case relay 406 remains operated through the normal contact of the thousands register wiper until such register is operated, as may be seen from an inspection Figs. 5 and 7. V

When the sending switch SS operatesto transmit the thousands digits, this digit is terminated, in a manner similar to the described termination of he single oiiice digit, when stop relay 406 pulls up over the stop conductor grounded by the' wiper of the thousands register; the remaining digits bcing similarly terminated in accordance with the setting of the remaining registers, respectively. It will be understood of course that y `switch are advanced at the end o the retransmission of the stations digit, the lower wiper of the switch closes a circuit through its last bank contact and over conductor 308 for switching relay 403, Fig. 5. Relay 403, at armature 414 disconnects conductor 46 from conductor 303 and connects'it to ground, ceasing a switch-through circuit to be mentioned subsequentl and at amature 415 opens the circuit o relay 404. Release relay 404 falls back and closes at armature 417 a restoring circuit over conductor 3041er the outgoing control switch OCS, and closes at armature 418 a release circuit over conductor 430 for the input-control switch ICS, the of- {ice register OR and the live registers shown in Fig. 7. Accordingly, the switches mentioned are restored to normal.

As a result of the above mentioned grounding of conductor 46 at armature 414 of relay 403, a circuit is closed over conductor 46 through a wiper and relay contact of the director selector DS, Fig. 1, armature 26 land its working contact, and armature 25 and its working contact for switching relay 23 of the trunk circuit TC. Relay 23 locks itself to conductor 6 at armature 30, and aat armatures 29 and 31 disconnects conductors 5 and 7 from the windings of relay 21 and connects them to the corresponding conductors 5 and 7 leading to the oflice selector OS. Line and release relays 21 and 22 now fallback and release relay 22 frees the director by releasing the director selector DS at armature 28.

When the director is freed, the switching relay 403, Fig. 5, falls back. y

Considering now the 'eiect produced by the trains ofyimpulses sent out by the director, the transmission of the oice digit Saresults in the operation of the oilice selector Fig. 1, which raises its wipers opposite the third level and selectsan idle trunk line, forexample, thel trunk line extending to the thousands selector M.

When the thousands digit is retransmitted the selector M responds and extends the connection to a hundred vselector in the corresponding group, for example, the hundreds selector D; when the hundreds digit is sent the hundreds selector D responds and extends the connection to an idle connector in the corresponding group, for example, the connector shown in Fig. 2, and reached by way of conductor 91-93.

When this connector is seized, line relay 101 pulls up over conductors 91 and 93 and closes at armature 121 a circuit for release relay 103. At armature 125 release relay 103 opens a point in the release-magnet circuit `and prepares the operating-magnet circuit;

it prepares the busy-locking circuit and switching-relay-tcst circuit at armature 124; prepares the ringing-return circuit at armature 123; and at armature 122 it places ground on conductor 92 to maintain the preceding switches operated.

When the tens digit is retransmittedby the director, line relay 101 falls back momentarily a `corresponding number of times and each time it does so it closes at armature 121 a circuit for vertical magnet 109, the circuit at the time of its first closure including armature 125 and its Working contact, contact of 011:' normal spring 112 and said spring, and series relay 104. By the operation of vertical magnet 107 the Wipers are positioned opposite the level of contacts in Which the called line terminates. Series relay 104 oper- -ates on the first impulse, and, being slow acting, remains operated throughout the entire series. At armature 126, relay 104 opens a point in the rot-aryfmagnet operating circuit and prepares a new circuit for itself and for the vertical magnet, which comes into play as soon as off-normal springs are shifted as they are upon the rst vertical step of the switch.

At the end of the vertical movement, relay 104 falls back and shifts the operating conductor lat armature 126 to the rotary magnet operating circuit. y

When the units digit is received each impulse delivered by line relay 101 at armature 121 and its resting contact is transmitted to rotary magnet 113, the circuit including armature 125 and its Working contact, off-normal springs controlled by spring 112, armature 126 and its resting contact, resting contact and armature 133, and armature 144 and.

its resting contact.' By the operation of rotary magnet 113 the Wipers 146-148 are rotated into engagement with the terminals of the desired party line. The slow acting relayr 107 operates in multiple with the rotary magnet 113 and remains operated throughout the entire rotary movement. At armature 138 relay 107 disconnects' test Wiper 147 from the' upper Winding of relay 108 andyconnects it through the resting contact and armature 142 to busy relay 106, and at armature 139 it places a shunt around the resting contact and armature 133 solas to maintain the rotarymagnet operating circuit intact regardless of any operation of busy relay 106 that may occur due to the encountering of busy test 'contacts by test Wiper 147 during the rotary movement. l .At the end vof the rotary movement, busy relay 106 is not Operated if the line is idle, but tact; and at armature 135 it `connects the lower 1,125

is operatedh over test Wiper 147 if the line is busy. In the latter case a lockingcircuit is completed for relay 106 including at armature 132 and its working contact when armature 148`f'allsback. Also, armature 133 holds the when called, busy relay 106 is not operated when the Wipers 146-148 come to rest on its terminals, and, when relay 107 falls back, a circuit is completed at armature 138 for the upper Winding `of relay 108 through' test wiper 147. This circuit includes armatures `124 and 132, and is. completed to battery y through the cut-off relay 149 of the called line. Relays 149 and 108 energize in series over this circuit and relay 149 clears the called .line of its normal attachments.

In the` connector, relay 108 closes alocking circuit for its lower Winding at the lightly adjusted armature 143; at armature 144 shifts ythe operating conductor from rotary magnet 113 to the operating magnet 162 of the station selector; armature 141 shunts its test Winding by placing ground directly on test Wiper 147 at armatures 140-and 145 connects up Wipers146 and 148 so as to prepare the ringing circuit.

l/Vhen the station selecting digit is received, the impulses of current from armature 121 and its resting contact of line relay 101 are delivered through armature 144 and its Working contact, of relay 108, to the operating magnet 162 of the station selector. Accordingly, the Wipers 164 and 165 are set on the corresponding set of bank contacts, in this case the first set, as the called station has a 66 cycle ringer connected between the negative line conductor and ground'. Relay 1407 is operated in multiple with the operating magnet 162 and it maintains a. branch circuit of relay 106 open at armature 137. At the end of the operation of the station selector,

relay 107 falls back and at armature 137 com j pletes a circuit for relay 106 including olf-- Wipers 164 and 165 of the station selector at.

armatures 130 and 136; completes at armature 131 the connection between conductor 167 and the upper Winding of relay-105 and including armature 153 and its Working con-` talking conductor through armature 144 and' its Working contact to the ring-back -tone conv ductor 166, Which conductor connected is the-11 regular 16-cycle ringing lead. Accordingly the calling subscriber bears the tone'and er y 66-cycle ringing current passes to the negaytive conductor of-the called line through the first bank contact and vwiper 164, working contact'and armature 130, restingv contact and armature 127, armature 140 and2 its working contact, and wiper 146 and the bank contact onwhich it is standing, a return path to ground from the positive conductor being provided through the-.positive bank contact and wiper 148, working contact and armature 145, armature 129 and its resting contact, armature 136 and its working contact, wiper 165 and the first associated bank contact, conductor 167, working contact and armature 131, armature 123 and its working contact and the upper winding of relay 105. There is no current iow over this return` ath at this time, however, owing to the fact t at the ringers on the party line are connected in` ground return circuits. The ringing current is intermittently applied to the ringing conductors by interrupter relay 252, Fig. 3, which relay is controlled by the interrupter 251, the ringing leads beingv connected to battery during the silent period so as to permit the ring-cut-of relay 105, Fig. 2, to be operated during the silent eriod.

When the calle subscriber responds by removing his receiver, he bridges the conductors of the called line with his receiver, transmitter, and calling device in series, whereupon a iow of current takes place over the abovetraced return circuit, energizing relay 105.

At armature 128, relay 105 closes a locking circuit for its lower winding, and at armatures 127 and 129 it disconnects the wipers 146 and 148 from the wipers of the station selector and connects them instead to the usual talking circuit of the connector including the battery feed relay 102. Talking battery is now supplied to the called station through battery feed relay 102, the talking battery for the calling station being supplied through line relay. 101. The calling and called subscribers may lnow converse with eac-h other.

When the conversationis over, the subscribers replace their receivers. lVhen the receiver is replaced at the calling substation, line relay 101 of the connector falls back,

A opening the circuit of release relay 103 and preparing the release magnet circult. When release relay 103 falls back it removes ground from release trunk conductor 92 at armature 122, whereupon relays 105`and 108 fallback. At the same time,ground is removed from the busy relay 'locking circuit at armature 124, and the upper winding of relay 105 is disconnected from conductor 167 at armature 123. At armature 125, relay 103 closes a circuit through off normal contacts 111 for release magnet 110 and through armature 134 and its working Contact for release magnet 163.

.necter and the station selector are restored to normal position in theusual manner. The circuit o release magnet 110 isopened at olinormal contacts 111 when the connector is restored to normal, and busy relay 106 falls back when its circuit is opened at olf-normal contacts 161 and opens at armature 134 a circuit of release magnet 163.

As a further result ,of the removal of the ground otential from release trunk conductor 92, t e selectors OS, M and C, as well as the calling line switch are released in the usual manner, and relay 23 of the trunk circuit TC falls back.

From the foregoing description it may be understood that when any other station on the party line shown in Fig. 2 is called the connector is set in the'same position as before, but the 'station selector is set in'some other position, depending upon the particular substation called, the arrangement being such that the `selected ringin current is applied to the negative side of t e called line if the station selector is set in any odd-numbered position, while the ringing current is applied to the opposite side of the line if the station selector is setin any even-numbered position. By this arrangement, the ringing leads are not connected to adjacent contacts in the bank of either wiper. The conductor 167 is opened at armature 123 of release relay 103 before the releasing operation starts so that there is no possibility of arcing at the bank contacts upon the return of the wipers 164 and 165,

as would ensue if the conductor 167 were left l connected up, or if adjacent contacts were connected to dllerent ringlng leads.`

Handling a reverting call connected between the negative side of the line and ground. Accordingly, when the connection to the reverting call switch is finally established, the reverting call switch must apply 50 cycle ringing current and 66 cycle ringing current alternately to the negative side of the line, as the reverting-call or ring-back switch shown in Fig. 3will do when its wipers are set upon the first set of bank contacts in the level shown in the drawings. In order to establish the desired connection, the arty line subscriber removes his receiver and then dials two digits common to all reverting calls, followed by the two digits required to set the ring back switch in the position necessary to give the combination of rings needed for a particular call being made, after which he replaces his receiver, as he is instructed todo. It will be assumed that the line switchof the calling line selects the trunk line extending tothe trunk circuit TC, Fi 1, and that the director Aselector DS selects t e director shown in the are raised opposite the proper level and are rotated into engagement with bank contacts 502, whereupon the sending operation is started in the manner hereinbefore described.

When the callingsubscriber dials the following two digits that are to control the setting of the rlng back switch, these digits are registered on the thousands and hundreds registers shown in Fig. 7.

When the lower wipers of the switch ICS is grounded by the upper'wiper of IOS at the end of the second digit a circuit is closed through the first Wiper 523 of the office register, the bank contact on which it is standing, the corresponding I.D.F. jumper, and over conductor 527 for relay 506. Relay 506 energizes and locks itself to release trunk conductor 46 at armature 509; opens the impulse wire leading to the magnet of the tens register Fig. 7, at armature 511; prepares a shortnumber switch-through circuit at armature 507; and at armature 510 connects the grounded conductor 527 to conductor 528, extending ground through the associated I.D.F. jumper to the third impulse stop conductor. At armature 508, relay 506 prepares a locking circuit for maintaining the seizure of the director independent of the maintenance of current flow over'` the calling line. This circuit is completed between ground and conductor 46 when the hundreds register goes off normal.

lVhen the calling subscriber hangs up his receiver after having finished dialling, relays 21 and 22, Fig. 1 fall back, and relay 22 re--` moves ground at one point from relay 32 and conductor 46, leaving conductor 46 grounded through the above mentioned locking circuit including armature 508, Fig. 6 and oil' normal contacts of the hundreds register, Fig. 7. As ground from the first contact in the set 502 of the ol'lice register Fig. 6, is extended to the third impulse stop conductor over conductors 527 and 528, and as the second and third contacts are cross connected on the I.DI.F. to the sixth and fourth impulse stop conductors, the three digits 3, 6, and 4 necessary to trunk the call to a ring back switch are transmitted in the usual manner, after which the outgoing control switch OCS (which has advanced one step at the end of the transmission of each digit) advances another step and arrives in 'its fourth position. The fourth code-digit position is sklpped in the usual manner.

The director now retransmits the' digits y registered on the thousands and hundreds registers, Fig. 7, the outgoing control switch being advanced one step at the end of the retransmission of-each digit. As a result, the

outgoing control switch lands in its seventh posltion at the end of the lretransmission of -the digit stored on the hundreds register.

.When this occurs, the lower wiper of the outgoing control switch prepares a circuitv through its seventh bank contact and the associated conductor, armature 507 of relay 506 and its working contact, conductor 308', and the resting contact for the switch-through relay 403, Fig. 5. This circuit is held open at armature 461 for an inter'al to give the ringback switch time to switcn through. When this circuit is closed, relay 403 energizes and closes a locking circuit for itself at armature 415, at the same time opening the circuit of release relay 404 with results similar to thosev i described hereinbefore. As afurther result of the energization of relay 403 a circuit similar to that hereinbefore traced is closed at armature 414 for the switching relay 23, Fig. 1. However, since the calling subscriber has already replaced his receiver, according to the foregoing assumption, and since relays 21 and 22 are deenergized as a result, the circuit includes armature 26 and its resting contact instead of armature 26 and its working contact and armature 25 and its working contact. When relay 23 operates it locks itself to releaase trunk conductor 6 at armature 30, and at armatures 29 and 31 switches the conductors 5 and 7 to the corresponding conductors 5 and 7 at the same time disconnecting the latter conductors from the outgoing control circuit of the sender.

In the director, when the hundreds register is released responsive to the grounding of conductor 430 by release relay 404, the off-normal contacts of the hundreds register remove ground from release trunk conductor 46 to which a ground connection has been maintained through armature 508 and its working contact, as above pointed out. When this occurs, switching relay 403, Fig. 5, and relay 32, Fig. 1, fall back and the director is free to handle another call.

rlhe etl'ectof the digits sent out by the director will now be considered. The oiiice selector OS 'responds to the first code digit 3 and seizes a thousands selector such as M; the seized thousands selector responds to the second code digit 6 and seizes a hundreds selector such as C; and the seized hundreds selector responds to the third code digit 4 and seizes an idle ring-back switch such as the one shown in Fig. 3. When such ring-back switch is seized, line relay 203 operates over conductors 94 and 96 and closes at armature 228 an energizing circuit for release relay 204. Release relay 204 prepares the switch for operation at armature 230 and 231; and at armature 229 places ground on release trunk conductor 95 so as to hold up the preceding switches.

As a further resultof the seizure of the ring-back switch, a circuit is closed for relay 202 responsive to the application of ground potential to conductor 95, which circuit includes the normally closed off-normal contacts 213. At armature 225 relay 202 prepares a locking circuit for itself, and at armature 226 it switches the associated operating conductor from the rotary magnet`211 to the vertical magnet 210.

When the digit registered on the thousands register, Fig. 7, is retransmitted in the manner hereinbefore explained, line relay 203, Fig. 3, falls back each time its circuit is interrupted by the director, and each time it falls back it closes a circuit for vertical magnet 210 at armature 218. This circuit includes armature 231 and its working contact, armature 239 and its resting contact, and armature 226 and its working contact. By the operation of the vertical magnet, the wipers of the switch are raised opposite the desired level of bank contacts. Series relay 208 is connected in multi le with vertical magnet 210 at this time an it operates and remains ope erated throughout the series of impulses on account of its slow-acting characteristic. At armature 240, relay 208 completes a locking circuit for relay 202 including the working contact and armature 225, before the initial circuit of the relay is opened at off normal contacts 213, as it is upon the first vertical step of the switch.

At the end of the lvertical movement, series relay 208 falls back and opens the locking circuit of relay 202 at armature 240, whereupon relay 202 falls back and shifts the operating conductor from the vertical magnet to the rotary magnet. A

When the ring-back switch receives the digit transmitted by the director in accordance with the setting of the hundreds register, Fig. 7, the impulses of current generated at armature 228 and its resting contact of line relay 203 are transmitted through armature 223 and its resting contact to the rotary magnet :with the result that the wipers 244-247 are rotated into engagement with the corresponding set of bank contacts. In the present case, the ringcrs of the calling and called parties are both connected between the negative line and ground and they are a 50-cycle ringer and a (i6-cycle ringer, respectively, as hereinbeforeassumed. Accordingly, the last series of impulses includes only a single impulse and the wipers 244-247 are positioned on the rst set of contacts of the level shown in the drawing. Series relay 208 is operated again during the rotary movement of the switch and it maintains the wipers disconnected during such movement at armatures 220-242.

When relay 208 falls back, it connects up wiper 247 at armature 242, whereupon the grounded lower winding of wiper 207 is energized through armature 235 and its resting contact and armature 242 and its resting contact. The circuit of relay 207 is completed to battery over the (i6-cycle ringing-current lead, which is connected to the first contact in the bank of wiper 247. Upon energizing, relay 207 completes at armature 237 a locking circuit for its upper winding to the conductor 251, grounded at armature 230; at armature 238 it opens the circuit of its lower winding; and at armature 239 it disconnects the working contact and armature 231 from the operating circuit and prepares a circuit throu h armature 234 and its resting contact for re ay 201.

Since, according to the previous assumption, the calling subscriber hangs up before lthe director has inished sending, and, since the director switches through shortly after the retransmission of the last stored digit, line relay 203 shortlyfalls back and closes at armature 238 a circuit through armature 231 and its working contact, armature 239 and its working contact, and armature 234 and its resting contact for relay 201. Relay 201 en! ergizes and at armature 222 comple/tes an auxiliary holding circuit for release relay 204.

At armatures 221 and 223, relay 201 discon- 4 neets conductors 94 and 96 from the windings of line relay 203 and connects them instead to armatures 224 and 227 of relay 202. Since, according to .the previous assumptien, both 'of the ringers involved in the present call areconnected between the negative side of the calling line and ground the bank contact that wiper 244 is on is dead and relay 202 is deenerg1zed,-tlie connections in the ring back switch being such that ringing current 1s normally transmitted back to the negative side of the line with relay 202 deenergized. It will be noted that relay 209 is connected through armature 241 and its resting contact, and wiper 245 and the bank contact on which it'is standing, with the interrupter 250. This interrupter intermittentl operates the ringing-current reversing re ay 209 so that it is operated during a given operation of the ringing interrupter relay 252 and is nonoperated on the following operation of the said relay, etc. With relay 209 nonoperated, and with interrupter relay 252 operated, ringing current over the 66-cycle lead is placed on the negative talking conductor throuh bank contact and wiper 247, resting contact and armature 243, resting contact and, armature 235, ring-cut-oi-control relay 206, resting contact and armature 224, and the working contact andarmature 221. When the ringing interrupter relay 252 is operated the next time, relay 209 is also operated and the ringing current sent out is from the 50-cycle ringing lead` through wiper 246 and the Working contact and armature 243. By this arrangement, the ringers at the calling and called substations are operated alternately.

When the called subscriber responds to the operation of his ringer by removing his receiver, a bridge is closed across the two conductors of the calling line, and, since the positive conductor is grounded, a circuit is closed from conductor 96, through the calling substation, and over conductor 94 for operatin the ringcut-oiicontrol relay 206 included in the ringing circuit. This relay at armature 236 closes a circuit for ring-cutoffl relay 205. At armature 233, relay 205 closes a locking circuit for itself; it opens the ringing circuit at armature 235, whereupon relay 206 falls back; and at armature 234 it opens the circuit of slow acting relay 201 and closes a circuit for release magnet 212. Release magnet 212 energizes and restores the switch to normal, whereupon the release-magnet circuit is opened at contacts 214. Slow-acting relay 201 (being slow acting so as to 've the release magnet time to operate) falls ack responsive to the opening of its .circuit atthe rest-ing contact of armature 234. At armature 222, relayv 201 opens the circuit of relay 204 and at armatures 221 and 223 it shifts the conductors 9 4 and 96 back to the windings oi. line relay 203 again. Line relay 203 now operates over the calling line in series with the transmitter bridge at the called substation, and at armature 228 it closes a circuit for relay 204 before the same has had time to fall back.

When the calling subscriber notes that his ringer has stopped operating, he removes his receiver, whereupon the conversation may take place in the usual manner.

When both subscribers have replaced their receivers at the end of the conversation, line relay 203 falls back and opens the circuit of release relay 204 at armature 228, and relay 204 falls back after a slight interval and at armatures 229 and 230 removes yground from conductors 95 and 251. Relays 205 and 207 now fall back. At armature '231, release relay 204 closes a point in the release magnet circuit, but `as the switch `has already been restored to normal the release magnet circuit is open at off-normal contacts 214.

Responsive to the removal of ground potential from conductor 95 the preceding portion of the connection is released in the usual manner.

Hang-up-tone reverting-call operation The hang-up-tone method of revertingcall operation will now be explained. When this method of operation is used, theterminals 215 and 216, Fig. 3 are jumpered together, with the result that when the director has finished sending, the hang up tone is sent back over the calling line and informs the calling subscriber that he may now hang up his receiver. Also, the locking connection, Figs. 6 and 7 to conductor 46` and including off-normal contacts of the hundreds register and armature 508.and its working contact is not provided, and, in Fig. 1, the conductor connected through armature 26 may be transferred'to armature 25, and armature 26 and its associated contacts may be eliminated.

When this modiication is used, the subscribers are instructed to dial the numbers as in the previous description, but to wait for the hang-up tone before replacing the receiver. In this case it is evident that the hang up tone cannot be heard until the ring back switch'has been set and until the switch-fV ing through relay 23, Fig. 1 has been oper# ated. Accordingly, the director is held up from 'ground supplied to conductor 46 through the director selector DS, from the working contact and armature 28, Fig. 1,

and when the switch-through circuit is enclosed it includes-armature 25 and its work`l ing Contact of relay 21, Fig. 1, as relay 21 is. still operated at this time.

Referring now to Fig. 3, when the ring back switch has been positioned on the necessary contacts, relay 207 is operated in the hereinbefore described manner and at armature 253 connects the common hang-up tone lead through armature 252 and its resting contact, and the jumper between terminals 215 and 216, to the lower talking conductor. Upon hearing this tone the calling subscriber replaces his receiver whereupon relay 203 falls back with the results hereinbefre described.

The remaining ortion of the operation is the same as descri d hereinbefore.

S'implzjed reverting-call operation When it is desired to reduce the complicacy y of the exchange equipment as much as possible, a still different operation may be employed. In this third case, the relay 506 Fig.

6 and its associated connections'may be eliminated, the conductors passing through normally closed contacts on relay 506 being arranged so that these contacts are by-passed.

In this case the bank contacts onvwhich the wipers of the'oiiice register OR are set when ner and the director is released. This switching operation occurs between successive digits dialled by the calling subscriber and without his knowledge, the calling subscriber being instructed to follow the two characteristic dlgits by the di its 3, 6, and 4, necessary to operate the switc les OS, M, C and two more digits to operate a ring back switch. Theseswitches respond directly to the control on his calling device instead of indirectly through the director as hereinbefore described. v

Meter operaon The meters 407-410, Fig. 5, will now be considered. It will b e noted that the meter 410v is connected between the free pole of battery and release trunk conductor 46. As a result, the meter 410 is operated eachl time conductor 46 is grounded responsive to the seizure of thedirector, and the reading of this meter indicates the actual number of times the director is seized and released regardless of the disposition of the calls responsive to which the seizures are made.

Meter 409 is arranged so that it is operated at armature 416 each time the switching relay 403 operates. This meter therefore gives a reading of the total number of. times the switching relay 403 is operated.

The meters 407 and 408 are arranged to be alternatively operated by the switching relay 403, depending upon the position of relay 40.2.v If the switching relay 403 operates because the director hasy completed its operation 1n handling a regular connection, relay 402 is not energized and meter 408 operates in multiple with meter 409. On the other hand, if the switching relay 403 operates merely to free the director on account of a delay in dialingafter the director is seized and either before or afterv a number has been partly dialed, relay 402 is in operated postion and meter 407. The manner in which relay 402 operates will now be briefly explained. The slow interrupter 401 is operating at a rate of speed which is slow lenough-to insure'that ample time is allowed for dialing at least one digit' between successive operations of the in- Iterrupter. The intermittently grounded lead controlled by interrupter 401 is connected up at armature 414 of release relay 404 when the director is seized. As soon, afterthis occurs,

as the conducting part of the interrupter comes under the associated brush, a circuit is completed through armature 414 and its working contact and armature 411 and its resting contact for the upper Winding of the two-step relay 402. When energized through its upper Winding alone relay 402 operates through its lirst step only, operating its firststep armature 412, but'not its second-step armatures 411 and 413. Armature 412 closes a locking circuit for relay 402 including conductors 306 and 307 in series with the lower contacts of relay 301, Fig. 4, the conductor weasel;-

307 being an extension of the grounded reof relay 402 remains short circuited, however, until the initial circuit for the upper winding is opened by the interrupter 401,3whereupon the two windings of the relay 402 energize in series, operating the relay through its second step. At armature 411, relay 402 opens a further point in its initial circuit and prepares a circuit for switching relay 403, and'at armature 413 it shifts armature 416 from connections with meter 408 to in connection with meter 4037. It will be remembered that relay 301 operates each time a series ofimpulses is received by the director. If a series of impulses is received the slow interrupter 401 closes again, relay 402 falls back because its backing circuit is opened and prevents the switching relay 403 from being operated, and the previously-described operation of relay 402 is repeated when the interrupter contacts again close. However,'if, at any time, no digit is received between successive operations of the interrupter a circuit is closed through armature 411 and its working contact for relay 402, switching the connection through at the trunk circuit TC in the hereinbeforedescribed manner and freeing the director. In this case, since armature 413 is in its alternate position meter 407 is operated instead of meter 408.

It will be noted that either of the meters 407-409 could be eliminated, if desired, in which case the equivalent of the reading of the eliminated meter could be readily calculated from the readings ofthe two remaining meters.' It is considered to be preferable, however, to provide the three meters as shown in the drawings, as in this way a defective reading on any meter may be discovered by comparing it with the readings of the other two. f

'It may be pointed out that-the difference in the readings of meters 409 and 410 indicates the number of calls abandoned before the call has progressed suiiiciently far for the director to be freed by the operation of relay 403.

Regarding the utility of relays 451 and 452 Fig. 5, it may be stated that these relays are provided in orderto enable the cut-ofi of the director to be revertively controlled.` When a callis made to a party line substation, an extra digit is needed to operate the station selector, for example the station selector shown in Fig. 2. Accordingly, the director is arranged so that it is automatically cut oil (switches through) as hereinbefore described when the number `contains a `stations digit. When a call is made through a connector not equipped with a station selector, however, the stations digit is omitted` and an arrangement similar to that disclosed in Fig. 8 of the copending application of Richardson et al. Serial Number 694,842,

lay 451 a circuit for relay 403, with the hereinbefore described results.

What is claimed is 1. In a telephone system, a plurality of Y ringing leads connected to different sources of ringing current, a ringing current selecting switch having a wi er and a bank of contacts arran ed to e connected with said ringing lea s, and means for preventing said- Wiper from short circuiting said ringing leads by distributing them amongst the contacts in said bank so that dead contacts are left in the bank between 4contacts that are connected to said ringing leads.

2. In a telephone system,l a trunk line, a register sender, means for connecting said trunk line with said register sender, means responsive to a particular setting of the registering portion of said register sender for locking said register sender in connection with said trunlrline, and means responsive to the operation of said sending apparatus under the control of said register for unlocking said register sender.

3. In a trunk circuit, a line relay, a release relay, a switching relay, a circuit for said switching relay through contacts o n said line relay and on said release relay when the line relay and release relay are operated, and circuit for said switching relay through contacts on said release relay alone when said release relay is non-operated.

4. In a. telephone system, a ring-back` switch arranged to be operated over a calling line and to remain operated after the receiver has been replaced on the calling line. and means including a source of tone current Vfor informing the calling subscriber when he may replace his receiver after having brought about the operation of the ring-back switch.

5. In a telephone system, automat-ic switches for setting up a connection, means for automatically holding up the connection after the same has been established up to a certain stage, a register sender for controlling the switches, and means in said register sender for holding up the connection in case the calling party hangs up before said certain stage is reached.

6. In a telephone system, automatic switches for setting up a connection, means for automatically holding up the connection between the hangin up of the receiver andv the completion of t e connection up to the said stage specified.

7. In an automatic telephone, systemin which the calling subscriber hangs up his receiver to start a revertive ringing operation and in which, register senders are used to set the switches involved in selecting the ringing equipment, means for giving the calling subscriber a distinctive signal to notify him when to hang up his receiver.

8. In an automatic telephone system in which the calling subscriber starts the operation of a selected ringing device by an act which is only cifcctive after the-device has been selected, and in which the selection is accomplished under control of a register sender subsequent to the operation of the subscribers dial, means for notifying the subscriber when the said act is to be performed.

9. In a director for use in a party line system including reverting call apparatus, a register adapted to be set in accordance with digits indicating a reverting call, and means controlled responsive to such setting for altering the director circuits to adapt the same for controlling said apparatus.

10. In a telephone system in which connections are set up under the control ot a calling subscribers calling device, means effective during the extension of a connection to hold the operated switches should the calling subscriber hang up his receiver, and other means effective after the connection is fully extended to holdup the connection after the calling subscriber has hung up.

- 11. In a telephone system, a ring-back switch, a register sender set under the control of a party line subscriber to operate said ringback switch to a position to ring a called subscriber on the calling line after the calling subscriber has hung up, means for locking said ringback switch in its operated position only after it has been set, and means for informing the calling subscriber when the ringback switch is set.

12. In a director for `handling reverting calls, means in said director responsive to a artial registration of a reverting call number for preparing a locking circuit for the director, and means responsive to the registration of the last reverting call digit for rendering said locking circuit etlective.

13. In a director, two successively operable registers, a locking circuit for said director, and means for rendering said circuit effective dependent upon a particular operation of the first register and upon the second register beingi sct.

14L`1`n combination, a ringing-current selecting switch having two wipers and a contact bank foreach w1per,a lurality of ringing leads, there being an o -normal osition ot' said switch assigned to .each of said ringing leads, half of said ringin leads beingr connected to alternate contacts 1n the bank of one wiper, the remaining ringing leads being connected to nonoui-responding contacts in' the bank of the other wiper so that no two adjacent contacts in the bank of either wiper are connected to ringing leads, a common return conductor connected at one end to the bank contacts in said switch not occupied by ringing lends and connected at the other end so as to form a return for the ringing current received over any one of the ringing leads, and means for maintaining said conductor open between its two ends at a time when said ringing current selecting switch is being moved over its contacts and for closing the connection between the two ends of such conductor when the switch is at rest in an off-normal position.

In witness whereof, I hereunto subscribe my name this 10th da of August, A. D. 1926.

LEON RD L. RUGGLS.

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