US2300829A - Calling line identification system - Google Patents

Description

Nov. 3, 1942. J. w. GooDlE'Rl-IAM CALLING AILNE IDENTIFICATIO N SYSTEM Filed March 22, 1940 14' sheds-sheet 2 TTQRNEV N0 3, 1942. J. w. GooDERl-IAM cALgING LINE IDENTIFICATION' SYSTEM 14 sheets-sheet 1 Filed March 22, 1940 @l ...Sos muzi mz3 sa ATTORNEY NovL 3, 1942- J. w. ooDEHAM CALLING LINE 'IDENTIFICATION SYSTEM 14 spams-sheet :s

,Lllllllll /NvENvron l* ai. MGOQDERHAM la lo lo l0 Filed March 22, 1940 Nov. 3., l9 42.

J; ymGQODERl-IAM CALLING LINE IDENTIFICATION SYSTEM `lll; Sheets-,Sheet 4 Filed Marh 22, -194Q /NvE/TOR J.y W GODERHA i A T TORNE V Nov. 3, 1942. J. w. GooDERHAM 2,300,829 v -CALLING LINE IDENTIFICATION SYSTEM Filed March-22, 1940 14 sheets-sheet 5 /NVENTOR J W GOODERHAM A T TORNE Y Nov.A 3, 1942. J. w. GooDr-:RHAM

cALLING LINE' IDENTIFICATION SYSTEM' 14 sheets-smet "7 File March 22, 1940 kan N .mi

Nov. 3, 1942.

J. W. GOODERHAM CALLING LINE IDENTIFICATION SYSTEM 14 Sheets-Sheet 8 Filed Marh 22, 1940 .235 12.23@ .32B mz3 .2563i /N V N TR s. nf GOODERHA M J. w. GOODERHAM CALLING LINE IDENTIFICATION SYSTEM Nov. 3, 19,42.

14 sheets-sheet 9 Filed March 22, 1940 /NVENTOR BJ. W GOODERHAM ATTORNEY Nov. 3, 1942. '.J. w. caoolaERl-mlvlA CALLING LINE ILENTIFICATION SYSTEM Filed March 22, 1940 14V Sheets-.Sheet A10 /Nl/ENTOR v BJI; w G0 00a-RHA M k QWSSK $54 ATTOR/VE Y Nov. 3, 1942. J. w; GooDl-:RHAM 25300829 CALLING LINE IDNTIFIGA'I'ION SYSTEM Filed March 22, 1940- 14 sheetssheet 11 BANK LEVEL REC/STER CIRCUIT /N VEA/TOR J. W GOODERHAM.. l er l I ATTvoR/vfy N0.v- 3, 1942- J. w. GooDERHAM CALLNG LINE IDENTIFICATION SYSTEM 14 Sheets-Sheet 12 Filed March 22, 1940 /NVENTOR m MM E ma G w@ JW n m l T A Nov. 3, `l942. J. w. GooDERl-IAM CALLING LINE IDENTFICATION SYSTEM 14 Sheets-Sheet 13 .Filed March 22, 1940 y/Nl/E/vrof? BJ. W GODERHAM NOV- 3, 1942 J. w. csooDERHArQl 2,300,829

CALLING LINE IDENTIFI-CATION SYSTEM Filed March 22, 1940 14 Sheets-Sheet 14 T0 LAST DECODER IDENT.' CIRCUIT B yew. M

`ATTORNEY Patented Nov. 3, 1942 y 2,300,829 cALmNc Linn IDENTIFICATION SYSTEM John W. Gooderham, Larchmont, N. Y., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March` 22, 1940, Serial No. 325,342

'21 Claims.

This invention relates to a telephone system and more particularly to a system in which it is desirable to register in equipment common yto a plurality of subscribers lines the identity of any one of the lines which may have originated a call.

In the establishment of toll calls in :systems equipped with automatic switching mechanisms, it is the usual procedure to permit subscribers to obtain access to a toll operatorsposition by dialing the digit zero or a suitable 'code of digits. The toll operator upon answering a call for toll service then secures from the calling subscriber the necessary information for completing the connection and the number of the calling subscribers line and then proceeds to complete the connection. Since it is necessary to charge a subscriber .for each toll call made during a billing period, the toll operator makes out a toll ticket for each completed call, which ticket has thereonr the calling subscribers line number, the number of the line called, the time when the called vsubscriber answered and the time when the conversation ended. These 'tickets are then used by the commercial department of the operating company in making out the regular bill for telephone service, the charges for toll calls made by any subscriber during the billing period vbeing computed from the tickets representing the toll calls and added to the amount to be charged such subscriber for local service connections.

In order that `toll calls may not erroneously be charged to subscribers who have not made such calls, the calling line number given to the toll operator is customarily checked by the toll l operator by the application of tone current over the connection established from the line to the operators position to a conductor associated with the calling line and by detecting the tone current through the connection of her headset receiver i to a number checking multiple of the calling line connected to that conductor. If the subscriber has vgiven his line number correctly to the operator, the tone current will be detected by 'the operator and the operator may then make out the toll ticket accordingly. y

It has heretofore been proposed to display the number of a calling subscribers line on a suitable lamp board located at or visible from the toll operators position thereby obviating the necessity for the calling subscriber to orally inform the operator as to the identity of his line. It has also been proposed to eliminate the services of a toll operator 'on calls to toll points which are not too remotely removed from the ldial switching 55 exchange area by providing facilities for automatically printing on va toll ticket all of the information which may be required for billing purposes, that is, the calling and called subscribers line identifications, the elapsed time of the conversation, etc.

It is the object of the present invention to provide calling line identification circuits whichare enabled to record the identication of any-calling line of an oice in a simple and inexpensive manner whereby such line identication record may be used either by a toll operator or byautomatic ticketing equipment in the production of a toll ticket for any toll call made by a subscriber.

As illustrative of the manner Ain which this object may be attained, the present invention has been disclosed in connection with a system in which all short haul toll connections to nearby toll points may be established by automatic switching equipment in response to the dialing of called line numbers by a calling subscriber and in which toll tickets for such calls are automatically printed or otherwise made, but` it is to be understood that the invention is equally applicable to systems in which all toll connections are established through the services of a toll operator and for which the toll operator makes out toll tickets in the usual manner. V'-Ihe invention has been illustrated in connection Wi-th telephone systems -employing step-by-step type switches but switches of other well-known types could equally well be employed. vAs illustrated, a subscriber, desiring a connection to a line terminating in an oice in the` nearby toll area,y rst removes his receiver from the switchhook whereby an idle line finder paired with a rst selector is started in search of the calling line and as soon as the line is found, the usual dial tone is transmitted.` Upon hearing the dial tone the subscriber then proceeds to dial the oiiice code and numerical digits of the wanted line number. Inv response to the dialing of one or more of rthe lofce code digits, the selector switches of aswitching train including the first selector switch are opera-ted to extend a connection from the calling line to an idle automatic ticketing trunk, accessible from al1 lines of the oice in which the calling line terminates, over which trunka connection may be further extended to the oice in Awhich the wanted line terminates. l

Immediately following the seizure ci 'the trunk,

isters for registering the remaining digits of a called line number dialed by the calling subscriber. Since, however, a digit dialed by a calling subscriber might be lost during the time elapsing from the seizure of the trunk and before the idle sender becomes connected with the trunk, the trunk is provided with a digit register for registering the digit dialed following the last code digit dialed to reach the trunk. Since the trunk may be seized in response to the dialing of one, two or three code digits, this register may register either the second or third code digit or the thousands numerical digit. As soon as the iirst digit has been registered in the sender, which digit may be either the third code digit,

grouped first with respect to all the line finders serving each group of two hundred lines and secondly with respect to groups of five such lineiinder groups to form ten master groups each serving one thousand lines. Thus the decoder identification circuit rst determines the master group of one thousand lines and makes a registration thereof and then determines the lineiinder group of two hundred lines and makes a registration thereof by detecting the tone current applied to the sleeve conductor of the line finder employed in establishing a connection. The rethe thousands digit or the hundreds digit, an

. idle decoder is associated with the sender over a decoder-connector and the decoder is associated directly with the trunk over a trunk decoder-connector. Thereupon office code identifying equipment associated with the trunk transfers to registers in the decoder information regarding the oioe code digits dialed to reach the trunk and if office code digits have been registered by the trunk register or by the first register of the sender, such registration or registrations are also transferred to the decoder whereby the decoder thus receives all of the information necessary regarding the office designation of the desired line. This information is then transferred to control registers of the sender which are instrumental in controlling selector switches to extend the connection from the trunk to the oiiice in which the wanted line terminates and in controlling a ticket printer individual to the trunk to print the called oiilce code digits on a toll ticket. The sender also registers the remaining numerical digits dialed by the calling subscriber and in accordance with'such registrations directs the setting of selector switches in the called ofl'ice to complete the connection, such numerical digit registrations also being effective to control the printer to print such numerical digits on the toll ticket. For controlling the ticket printer in accordance with the Vcode and numerical digit registrations made in the sender, the sender becomes associated with the trunk over a trunk sender-connector.

Since the trunk circuit, the called ofnce code digit identifying equipment of the trunk circuit disclosure of the discussion of the present invention, they have been disclosed schematically herein. For a more detailed disclosure thereof,

- reference may be had to the copending application of A. J. Busch, Serial No. 325,304I filed March 22, 1940.

Associated with each decoder and preferably forming an integral part thereof is a calling line identification circuit comprising a plurality of register circuits for registering the several elements of the line identiiication of any calling line in the oiilce. The identification circuits of all decoders have common access to an identification circuit which has access to the sleeve conductors of all line finders and to the sleeve conductors of al1 lines of the oiiice. To identify a calling line, the decoder upon its seizure applies an alternating current signal to the sleeve of the ticketing trunk which is transmitted back over the sleeve circuit established to the trunk from the calling line. The line-iinder sleeves are maining stages of identification employ the calling line sleeve conductors by first determining Whether the calling line terminates in the upper or lower bank of a line finder of the detected two hundred line group and making a registration thereof, by then determining the level of the bank in which the line terminates and making a registration thereof, and finally by determining the particular terminal of the level in which the line terminates and making a registration thereof by detecting the presence of the tone current on the sleeve conductor of the calling line. These iive registrations thus identify the calling line on a line-finder terminal basis and may be employed to light lamps to display the calling line identification or as disclosed such registrations may be transferred to registers in the printer control circuit of the sender for controlling the ticket printer of the ticketing trunk to print the digits on the toll ticket.

The ticket printer may also be controlled following the response of the called subscriber and during the continuance of the conversation to print information on the toll ticket indicative of the duration of the conversational period.

The invention having been described in a general manner, reference may now be had to the following detailed description thereoftaken in connection with the accompanying drawings in which:

Fig. 1 shows schematically a plurality of line finders, grouped rst in master groups each serving one thousand lines and then into subgroups each serving two hundred lines and a plurality of lines terminating in different banks and bank levels of line finders of the subgroups of one of the master groups;

Fig. 2 schematically discloses in the upper portion thereof a train of selector switches over which a connection may be established from certain of the calling lines over a line finder having access thereto to a toll ticketing trunk such as is disclosed in Fig. 3 and in the lower portion thereof a part of the one thousand line group circuits of the calling line identification circuit which are instrumental in determining the master group of one thousand lines and the two hundred line subgroup thereof in which a calling line is located;

Fig. 3 shows schematically two automatic ticketing trunks belonging to different groups of such trunks and connector switches of the crossbar type by which a calling one of such trunks may be associated with an idle sender;

Fig. 4 shows schematically two senders to which all ticketing trunks have common access, trunk sender-connectors by means of which the printer control equipment of any sender seized by any trunk may be associated with the tape ticket printer of the trunk, a plurality of decoders, a decoder-connector for associating an idle one of said decoders with the sender taken into use by any trunk and a trunk decoder-connector for associating the seized decoder directly with the calling trunk for enabling the decoder to receive from the trunk information relative to the called oiice code digits dialed by a subscriber;

Fig. 5 discloses in the left portion thereof the bank and level determining portion of the calling line identication circuit which is instrumental in determining the line-finder bank, the bank level and the terminal of the level in which any line terminates and in the right portion thereof switching relays for successively rendering different portions of the circuits of Figs. 2 and 5 effective;

Fig. 6 discloses in the right portion thereof otherV switching relays and in the left portion thereof groups of amplier and detector tubes connectable to the several portions of the identifying circuit through the operation of the switching relays of Fig. 5 for detecting the presence of tone current on the line-finder sleeve conductor and line sleeve conductor of any connection established by a calling line and register relays associable with the detector tubes;

Fig. 7 discloses a timing circuit associated with the circuits of Fig. 6; Y

Fig. 8 discloses a register circuit for registering the particular one thousand line group in which any calling line is located;

Fig. 9 discloses a register circuit for registering the particular line-iinder group in which a calling line is located;

Fig. l shows a register circuit for registering the line-finder bank in which a calling line terminates;

Fig. 11 shows a register circuit for registering the line-finder bank level in which a calling line terminates;

Fig. 12 shows a register circuit for registering the terminal of the line-finder bank level in which a calling line terminates;

Fig. 13 shows multicontact relays for connecting the sleeve conductors of groups of two hundred lines through the contacts of multicontact relays of the thousands line group connector circuit of Fig. 14 to the amplier-detector circuits, to the bank and level determining circuits of Fig. and to the line-nder group register circuit of Fig. 9;

Fig. 14 shows multicontact relays of the thousands group connector circuit; and,

Fig. 15 is a diagram indicating how the other figures of the drawings should be arranged to completely disclose the invention.

The line iinders schematically illustrated in Fig. l are of the well-known step-by-step type each having two brush sets one of which has access to an upper bank of terminals in which one hundred lines terminate and the other of which has access to a lower bank of terminals in which a second one hundred lines terminate. Each group of two hundred lines is accessible from a subgroup of line nders, an idle one of which is started upon the initiation of a call from any line of the group. The ve subgroups of line iinders serving a master group of one thousand lines are grouped together, two of the subgroups of line finders serving the No. 1 and No. 5 two hundred line subgroups of the' No'. 0 thousands master group of lines being indicated by numerals ISI and |05 and two 'of the subgroups of line nders serving the No. 1 and No. 5 twohundred line subgroups of the No. 1 thousands master group of lines being indicated by the numerals Hi and H5'. Other'subgroups of Llo line iinders serving other subgroups of such master groups and subgroups of line nders serving the other eight master groups would be similarly provided. l

To simplify the disclosure, the circuits of the line iinders have not been disclosed in full and with the exception of line iinder |06 only the sleeve conductors of the line finders, which are essential to the understanding of the invention, have been disclosed. The sleeve conductors of the subgroups of line nders of the No. 0 master group have branches which appear in contacts of multicontact relays of the thousands line group and line-finder subgroup determining circuits of Fig. 2. The sleeve conductors of the subgroups of other line nders of other master groups have branches which appear in contacts of relays of other thousands line group and linefinder subgroup circuits similar to that disclosed in Fig. 2. The sleeve conductors of al1 lines are connected over terminals on a terminal block i390 to the contacts of groups of two hundred line connector relays of Fig. 13, four multicontact relays such as |325 being provided for each two hundred line group of lines. By the interpolation of the connecting block i399, it isv possible to terminate the line sleeve conductor of a line on the contact of one of these relays appertaining to a bank level and terminal position indicative of the tens and units digit of the line number regardless of `whether that line actually terminates in that particular bank level and terminal position.

Each line nderis paired with a first selector switch 20B which has access to groups of trunks terminating in second selector switches such as 26| which in turn have laccess to groups of trunks terminating in third selector switches 292. These switches may be of the well-known step-by-step type and may be controlled by a calling subscribers dial to establish local connections or to establish a connection to an idle automatic ticketing trunk such as is disclosed at 300 in Fig. 3, should the subscriber desire a connection to a subscribers line which terminates in the toll area adjacent to the exchange area in which the calling line terminates. As disclosed, the automatic ticketing trunk may be seized by a third selector in response to dialing the three office code digits of a Wanted line, but it is to be understood that the same trunk may be seized from the banks of rst or second selector switches in response to dialing the iirst or the iirst and second oflice code digits of lines terminating in other omces as fully set forth in the application of A. J.

Busch hereinbefore referred to.

The cross-bar sender-connectors 328 and 32| of Fig. 3, the decoder-connector 429, the trunk decoder-connector 44D and the trunk senderconnectors 46|) and 479 of Fig. 4 may be of the same general type as are employed in the crossbar system and as are disclosed, for example, in Patent 2,089,921, granted August 10, 1937, to W. W. Carpenter. The senders, two of which are schematically disclosed by boxes MBU and di@ of Fig. 4, may be of a well-known type provided with registering mechanism for registering digits of wanted line numbers dialed by calling subscribers and with pulsing mechanism for controlling the setting of selector switches in accordance with such registrations to extend a connection from a seized ticketing trunk to a wanted line. Each sender is also provided with a printer control cir'- cuit for controlling a ticket printer individual to the trunk with which a sender has become associated to print on a toll ticket information with respect to the identity of the calling line and the identity of the called line. For assisting a sender in controlling the establishment of a desired connection, a plurality of decoders is provided, indicated by the boxes 400, 485 and 490, an idle one of which may become associated with a sender over the decoder-connector 420. Each of these decoders has associated with it acalling line identification circuit, the identification circuit associated with decoder 490 being illustrated in detail in Figs. 5 to l2, inclusive. The calling line identication circuits disclosed in Figs. 2, 13 and 14 are individual to an exchange office of ten thousand lines and are common to all of the decoders.

To more clearly set forth the novel features of the invention, it will be assumed that the calling subscriber whose substation is indicated by the numeral |00 initiates a call for a toll connection to a subscribers line terminating in an o'ice in a toll area to which the calling subscriber is permitted access by dialing. Upon the removal of the receiver from the switchhook, an idle line finder having access to the two hundred line group in which the calling line is located is started in search of the calling line in the wellknown manner. It will be assumed that the calling line is located in the No. 0 thousands line group of the oiiice and may be reached by a line finder of' the No. 5 line-finder group of the No. 0 thousands line group and that line finder |06 is started. It will also be assumed that the calling line terminates in the No. 2 terminal of the upper or No. 0 level of the upper bank of line iinder |06. When the line finder has found the calling line, the usual dial tone is transmitted to the calling subscribers line to inform the subscriber' that his line has become connected with a first selector switch and that he may, therefore, commence dialing the digits of the wanted line number.

It will be assumed that the line with which the calling subscriber kdesires a connection is located in a distant office which may be reached over an idle automatic ticketing trunk and that this trunk is reached over a first selector 200, a second selector 20| and a third selector 202 in response to the dialing of the three oice code digits of the desired line number. It will further be assumed that the trunk 300 of Fig. 3 is idle and that following the setting of the third selector 202 in response to the third office code digit dialed, this trunk is seized. Immediately following its seizure, it becomes associated with an idle sender, such as sender 400, over the sender-connector 32|. The calling subscriber may have proceeded to dial the next or thousands digit of the desired line number before the idle sender became associated with the trunk to receive the next digit dialed on one of its digit registers. The trunk is therefore provided with a digit register 3031 individual thereto which is rendered available to receive the dialed digit immediately following the seizure of the trunk. In the case assumed the thousands digit will be registered by the trunk register and the remaining numerical digits dialed by the calling subscriber will be thereafter registered by registers of the sender.

As disclosed more fully in the application of A. J. Busch hereinbefore referred to, the trunk 300 may also be seized directly from a first selector on calls to other oices in the toll area in which case the trunk is seized in response to the dialing of the first oice code digit. The

second code digit dialed is then registered by the trunk register and the third code digit and all rnumerical digits are then registered in the sender. -The trunkmay also be seized from the banks of second selector switches on calls to other oflices in the toll area in which case the trunk is seized in response to dialing the first two office code digits. The third code digit is then registered by the trunk register and the numerical digits are registered in the sender. In order that information regarding the one or more code digits dialed to reach the trunk may beI recorded for later use in controlling the extension of the connection from the trunk to the called oice, and for controlling the printing of a toll ticket, the trunk is provided with a called oflice code identifying circuit 302.

When the sender 400 has registered one digit which in one of the cases previously discussed may be the third code digit, the sender is assured that all of the code digits have been dialed and that information with respect thereto has been recorded in the called omce code identification circuit 302 or in the identification circuit incombination with the trunk register and a register of the sender and then proceeds to associate itself with an idle .decoder over the decoder-connector 420. The decoder-connector comprises a plurality of multicontact relays one for each sender and one for each decoder. If, as assumed, the decoder 490 is the first one available for use, relay 42| individual to the sender 400 and relay 422 individual to the decoder 480 will be operated to extend control conductors from the sender to the decoder. Over one of these conductors the sender informs the decoder as to which trunk group the trunk 300 is located in and proceeds to operate a multicontact relay 44| of the trunk decoder-connector 440 which has access to the trunk. If the decoder is successful in its attempt to seize the connector 440, it will establish a connection over the decoder-connector 420 through the sender 400 and over a cross-point of the sender-connector 32| for operating relay 306 in the trunk. This relay upon operating causes the operation of relay 442 in the trunk decoder-connector 440. With relay 30S of the trunk and relays 442 and 44| of the connector 440 operated, control conductors are extended from the called olice code identifying circuit 302 and the terminal bank of the digit register 303 of the trunk to the decoder for transferring information concerning the oflice code digit or digits dialed to reach the trunk and the code .digit or thousands digit registered by register 303.

If three code digits were dialed to reach the trunk 300, the entire information concerning those digits will be furnished to the decoder from the oflice code identifying circuit 302 and the thousands digit registered by the trunk register 303 will also be transferred to the decoder. If two code digits were dialed to reach the trunk information concerning these digits will be furnished to the decoder from the office code identifying circuit 302 and the third code digit registered by the register 303 will be transferred to the decoder and if but one code .digit was dialed to reach the trunk, information concerning this digit will be furnished to the decoder from the office code identifying circuit 302 and the second code digit registered by the register 303 and the third code digit registered in the sender will be transferred to the decoder. Having received the `code digit information, the decoder may make a translation thereof if necessary and proceed to transfer the information which it has received or the translated information to l.registers of the sender. The sender upon receiving the oce code information proceeds to control selector switches (not shown) to extend a connection from the trunk to the wanted oiiice and to control selector switches in accordance with the setting of its numerical registers to further extend the connection to the wanted line. The registration of the on'ice code and numerical digits of the wanted line in the sender is also eiective in conditioning the printer control circuit 40I associated therewith for later -controlling the tape ticket printer 304 of the trunk 300 over the trunk sender-connector 460 having access to the group of trunks in which the calling trunk 300 is located. For this purpose relay 301 of the c-alling trunk is operated over a -cross-point of the sender-connector 32| froin the sender and in operating causes the operation of multicontact relay 46| of the connector 400 which Calling line identification Following the seizure of the decoder a starting ground is connected to conductor 49| thereby causing the operation of start relay 800 of the identification circuit forming a part f decoder 490. Relay 800 upon operating supplies oiT-normal ground to the register circuits vof Figs. 8 to I 12, inclusive, and establishes an operating circuit for start relay SI I extending from battery through the winding of relay SII, conductor 8I2 of cable 100 extending to the timing 4circuit of Fig. 1, a contact of relay which is normally operated, conductor 8I3 of cable 100, back contact of relay 8I4, thence serially over the upper back -contacts of register relays 80| to 8I0, inclusive, conductor 8I5, No. 5 back contacts of advance relay |220, conductor 816, outer lower back contact of repeat test relay SI1 to ground at the inner lower front contact of start relay 800. It will be noted that this circuit will be closed only if the register relays 80I to SID of the thousands group register circuit are normal indicating that they are in condition to receive a registration and if relay 10| is operated indicating that the timing circuit of Fig. 1 is in normal condition and that the tone responsive register relays to BIB of the identification circuit are unoperated. It will be noted that under normal conditions, relay 10| is held operated in a circuit from battery over the upper back contacts of relays 60| to 6I0, in series, conductor EII, upper back contact of relay 102, winding of relay 10|, lower back contact of relay 103, conductor 104 to ground at the back contact of relay 649.

Relay 8II upon operating locks over its middle lower front contact and the lower back contact of relay 8 I1 to ground at the inner lower contact of start relay 800; closes a circuit for progress lamp SIS to indicate that the identification circuit has been started to register the thousands group identification digit of a calling line, which circuit extends from battery, through lamp BIS, upper front contact of start relay 8| I, conductor 8I9, upper back contact of start relay 9| I, conductor SIS, upper back contact of start relay |0I I, conductor IOI9, upper back contact of start relay I I I |,'conductor I I I9 to .ground at the upper back contact of start relay I2I I; ,prepares at its inner lower front contact a locking circuit for any subsequently operated register relay `of the group to BIO; prepares at its lower front contact a locking circuit for advance relay S20 and establishes a circuit from battery over the upper back contact of relay 820, the inner upper front contact of relay BII, conductorSZI to Yground through the winding of cut-in relay 203 in the thousands group identiicationV connector circuit disclosed in the right portion of Fig.`2. .This connector circuit has access to a group identification circuit individual to the calling office and common to all decoders comprising a plurality of multicontact relays such as 2I0 to ZIE, etc., having access to the sleeve conductors of all vline finders in the oiilce and ten one thousand group and line-Ender subgroup identification circuits, that one appertaining to the No. 0 thousands group of line finders serving the No. 0 thousands line group being disclosed in full and the similar circuits appertaining to the No. 1 thousands group of line nders serving the No. l thousands linegroup being indicated by the box 2I6.

If the thousands group identication circuits have not been taken for use by another decoder and therefore neither relay 204 nor 205 individual to other decoders is at the time op-erated, a circuit for relay 20E and other similar relays connected in parallel therewith will therefore be closed from ground over the upper back contact of relay 205, upper back contact of Vrelay 204, upper front contact of relay 253, winding of relay 206 and lower back contact of relay 200 to battery and relay 206 and the multiple connected relays upon operating will lock over their inner lower front contacts to battery independently of relay 200. At its lower normal contact relay 253 removes operating ground from the windings of relays 2&4 and 235 to prevent their subsequent `operation thus preventing more than one decoder from simultaneously seizing the connfnonr thousands group identification circuits. At its four upper contacts relay 200 establishes obvious circuits for multicontact relays 2|@ to 2I3 which upon operating connect the line-finder sleeve conductors of all line finders serving theY No.V 0 thousands group of line to the No. 0 thousands group identifying circuits and at its four lowercontacts establishes circuit for four multicontact relays 2id to 2I5, of which only two are shown, which upon operating connect the line-finder sleeve conductors of all line finders serving the No.. 1 thousands group of lines to the` No. l thousands group identifying circuits indicated by the box` 2 I 6. Other relays not shown which were operated in parallel with relays 20S similarly cause ythe operation of other groups of multicontact vrelays to connect the sleeve conductors of other groups of line iinders serving the Nos. 2 to 9 thousands groups of lines to other thousands group identifying circuits similar to that disclosed.

When all of the multicontact relays have become operated a chain circuit is established from ground over their upper 'front contacts to battery through the winding of relay 209 whichi at its back contact opens the initial operating circuit for relay 200 .and other multipled relays and at its upper iront contact establishes a circuit from ground thereover over the inner 'upper front contact of relay 206,. conductor 500 to battery through the winding of switching relay 592 and in parallel therewith over conductor 5cl to battery through the winding of switching vrelay SI2. With relay 502 operated, the input circuits of the ten amplifier-detector circuits of Fig. 6, the No. of which is fully disclosed in the dot-dash rectangle 635 and the Nos. l and 2 of which are partially indicated by the rectangles 62| and 622, are connected over the contacts of relay 502 and the conductors of cable 223 to the ten thousands group identifying circuits of Fig. 2 and the circuits controlled by relays 65|, 652 to 6|0,.from the anode relays 53| to E40 of the amplifier-detector circuits are connected to the operating windings of register relays 85| to SIB of the thousands group register circuit of Fig. 8.

Each amplier-detector circuit, for example circuit 63B, comprises an input transformer 6|3, a pentode type amplifying tube GIA, a detector tube SI5 and an anode relay 542. The anode relay of each circuit is a polarized relay normally held against its bacl: contact by a secondary polarizing winding. As disclosed, the filaments of all amplifier tubes are heated in a series circuit from battery GIS, the filaments of all detector tubes are heated in a series circuit from battery 5|? through the resistance network EIS, and grid biasing potential for all detector tubes is derived from battery SI1 and resistance network 6|8. But preferably two filament heating circuits each supplying the filaments of five amplifying tubes and two lament heating circuits and grid biasing networks each supplying the heating current and grid bias for ve detector tubes would be provided. Battery GIS supplies anode potential through the upper windings of the anode relays such as BIBB to the anodes of all detector tubes and through resistances such as 620 to the anodes of all amplier tubes.

Relay 6|2 upon operating establishes a circuit from ground over its No. 3 contacts, conductor 822 of cable 823, inner lower back contact of relay 8|'| to battery through the winding of relay 824 which operates and connects current from the 13S-cycle source 825 to conductor 862 whichl is at the time connected through the decoderconnector 420, sender 450 and sender-connector 32| to the sleeve conductor 398 of trunk Sl and thence over the sleeve conductors of the connection .established from the calling line lili] over the selector switches 250, 25| and 232 to the sleeve conductor |01 of the line finder |05 which has served the connection and over the sleeve brush |59 of such line nder to the sleeve conductor |08 of the calling line. At its No. l contacts relay SI2 also establishes a circuit from ground over such contacts, conductor '|65 to battery through the lower Winding of relay 65| and in parallel therewith through the winding of relay 153. Relay '|03 operates to release relay Il thereby opening the initial starting circuits for relays SII, 9H, etc., of the register circuits, to prepare an operating circuit for any one of the tone responsive relays 55| to BH3 by connecting ground over its outer lower front contact, over the upper transfer contacts of relay 'F55 and conductor 'I to the armatures of the anode relays of the amplifier-detector circuits and to perform other functions to be later described. Relay 64| being marginal does not operate at this time.

With alternating current now applied to sleeve conductor |81 of line nder |55 which is located in the No. 5 line-finder group of the master group serving the No. 0 thousands line group. current now flows therefrom over the next to upper front contact of relay 2li), through condenser 2li, resistance 2|8, primary winding of the No. 5 subgroup transformer 235 to ground through the primary winding of' theNo. `0 thousands 1 line group transformer 220. Transformer 235 is ineffective at this .time since its secondary windings are in open circuits but transformer-22|) isl effective toinductvely apply the tone current upon the primary winding of input transformer 6|3' of the amplifier-detector circuit 639 since switching relay 5612 has been operated, over a circuit extending from the'right terminals of the secondary windings of transformer 22D, inner left back contact of relay 22|, conductor 222 of cable 223, next to uppermost contacts of relay 502, conductor 503, Yprimary windings of input transformer 6|3, conductor 554, upper contacts of relay 552, conductor 224 of cable 223, next to inner left back contact of relay 22|, to the left terminals of the secondarywindings of transformer 220. Thus current is impressed by transformer SIS upon the input circuit of amplifier tube 5M, is amplified by this tube and tube SI5 detecting the presence of the' current operates the anode relay E40 to close its contacts.

It will be recalled that relay '|03 of the timing circuit was operated following the operation of switching relay 6 I2 and therefore upon theoperation of anode relay 640 a circuit is closed from groundapplied to conductor Till by the operation of relay 163,` over the contacts of relay 640, through the winding and transfer contacts of relay SIO, conductor '|08 to battery at the upper back contact of relay 105. Relay 6H] thereupon operates, locking over its transfer contacts to battery. Y Y

The timing circuit of Fig. -7 is used in connection with the amplifier-detector circuits in making each of the veidentication tests. Due to using the sleeve circuits of line nders and-selectors for conducting the identification tests, there may be a number of surgesv involved in the sleeve circuit during the making of the tests. These surges are due to the charge and discharge of the condensers connected to the sleeve circuits, such as condenser 2|'|, because of calls being initiated and disconnected on lines being served by the line finders involved in each test.

Also, surges will be involved due to selectors hunting past selector bank terminals over which an identification test is being made. Also very short surges would be involved due to the bridging conditions at the connectors and at the linender banks `of the sleeve circuits under identication. In order to avoid false operation of the register relays 60| to 6||l at the outputs of the amplifier-detector circuits, the connection of the circuits from the contacts of the anode relays such as 64|) to the register relays is controlled by the timing circuit. v

This timing circuit is provided with three cold cathode tubes 109, 'IID and for which anode current is supplied 'from the source ||2 over conductor '|20 to the windings of their associated anode relays H3, 'H4 and H5 bythe operation of relay 103. Relay '|03 when it operated started the first timing cycle by connecting ground to the right cathode of tube '|09 over the lower normal contacts of relay '186, by opening at its upper back contact the short circuit or discharging circuit through resistance '|32 for the timing condenser 'H6 associated with the tube '|09 and by establishing a charging circuit for condenser 'I l 6 extending from ground through the condenser, resistance 1|7 and the inner lower contact of relay '|03 to battery 1|2. After an interval in the order of one-tenth second, the condenser '||6 becomes charged and potential from

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