US2370736A - Telephone system - Google Patents

Description

L.. E. KITTREDGE 2,370,736

TELEPHONE SYSTEM Filed March l5, 1940 ll Sheets-Sheet l March 6, 1945.

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TELEPHONE SYSTEM Filed March 13, 1940 l1 Sheets-Sheet l0 Hulvonfo's ofc/r FIG' /0 /NVE/v TOR. LE K/TTREDGE A 7' TORNE'V March 6, 1945. L, E. KITTREDGE TELEPHONE SYSTEM 1940 ll Sheets-Shee ll Filed March l5,

A T TOR/VE V Patented Mar. 6, 1945 TELEPHON E SYSTEM Linus E. Kittredge, Port Washington, N. Y., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation o! New York Application March 13, 1940, Serial No. 323,666

(Cl. 179-71) A 10 Claims.

This invention relates to telephone systems and more particularly to automatic recording equipment for such systems that embodies means for making a permanent record of the calling line number, the called line number, and the duration of a connection automatically established between two lines.

At the present time it is well known that charges for local telephone service are usually recorded upon message register meters associated with the calling lines regardless o! whether the telephone system o! which these lines form a part is a manual, semiautomatic or full automatic system, and that said meters are operated when the called subscribers remove their respective receivers from their switchhooks as evidence o! completed connections.

Recent advances in the automatic telephone art, however, make it desirable to have subscribers dial directly the ofce and number oi wanted subscribers who are located outside the local area. As is well known, toll calls are timed and ticketed by an operator, one of whose duties ls to make out a ticket for each call. Upon this ticket are recorded the calling and called line numbers and the duration of the connection so that, when the monthly bill for the subscriber is made, the entries on these tickets are included as separate items thereon. Timing and ticketing, however. involve considerable delays at `the position through which the line of a calling subscriber, seeking a toll connection, must be routed before completion thereto by manual or semiautomatic means, and such delays have a tendency to cancel a portion of the eiliciency oi operation gained by establishing connections with switching mechanisms controllable from a sending device at the calling station.

My invention is intended to overcome this obstacle of manual recording of the data oi a toll connection by providing facilities at the central oflice that will automatically record the calling and called line numbers of the two lines involved in a toll connection together with a record of the duration of the conversation, thus eliminating the necessity of a manual recording position at the toll switching center and thus making possible the logical extension oi the principle oi mechanical switching to distant toll areas. The present invention, therefore. in its adaptation and application to a telephone plant, has for its broad cb ject a system of apparatus and operating circuits whereby the details of a toll connection such as, for example, the number of the calling line, the

number oi the called line and the duration oi the conversation are automatically recorded by adevice associated with one oi' the trunks of the connection,

Une oi' the features of the invention s an identifying selector which is used to locate the terminals of the calling line subsequent to the initiation of a call, a settable register which, cooperating with said selector, is operated to register the movement o! the selector in terms o! the terminals travelled over to reach the terminals of the calling line, and a series oi' pulsing switches operatively responsive to the setting ci' said register to transmit to the recording device a group or groups of pulses indicative of the calling line terminal number as evidenced by the number oi' steps taken by said selector and registered in sai settable register. Y

Another feature o! my invention is to be found in the use of a second settable register which' is adapted to respond to the transmission oi the called pulse dial code from the local register sender into which it is registered following the dialing of the same thereinto from the impulse 2s device at the calling line, in combination with another series of pulsing switches operatively responsive to the setting ot said register to transmit to the recording device a plurality oi' groups of pulses indicative oi the called line designation.

Yet another feature oi my invention is a connector circuit common to a group of trlmks and switching selectors over which toll connections are established, in which may be incorporated the two settable registers and pulsing switches mentioned above, thus ail'ording considerable economy oi.' equipment in that said registers may be utilized in common by a plurality of trunks and switching selectors. p

Yet another feature of the invention is to be found in the operation oi one recording device by the connector in causing the production of a permanent record of the calling line designation over one connection with which said connector is operatively associated, and simultaneously therewith in causing the operation of another recording device by said connector in causing the production oi' a permanent record o! the called line designation over another connection with which said other recording device is associated. By virtue of this double connection to two separate calling lines in diilerent stages of call establishment. connector holding time is reduced to a minimum and, therefore, less connector circuits for a given group of switching selectors and outgoing trunks will be necessary than otherwise would be the case if a connector were utilized for one connection at a time.

One embodiment of the invention which is herein described by way of illustration is adapted for operation with mechanical switches of the well-known panel type which are used to extend subscribers lines over tandem routes and the invention comprises, broadly, an identifying selector for a given group of line-finder switches, a connector circuit available to a plurality of groups oi line-finder switches and outgoing trunks connectable therewith, and including two settable registers and pulsing switches for translating the setting of said registers into suitable groups oi impulses indicative of the separate settings, and recording means in each oi' the outgoing trunks accessible to the line-iinder switches which are responsive to the impulses transmitted thereto from the pulsing equipment of a connector and also responsive to timing equipment in the trunks themselves for measuring the duration of the connection thereover.

Before proceeding with an outline o! the invention it is advisable to point out the general operation oi so-called tandem connections, which are telephone connections established between two subscribers located in diii'erent telephone omces that are joined by trunk lines extending to and radiating from a tandem oflice. Thus when a subscriber in a local omce dials a number in another omce which is reached through the tandem center, a line-iinder switch becomes connected to the line in the usual way and a tree local register sender becomes connected thereto to receive the dial impulses o! the called number. The register sender, in response to that portion oi' the called number which designates the called oiiice, directively controls the operation of a district selector in selecting a, trunk line which terminates as a selector in the tandem otiice and having access to groups oi trunk lines leading to various oices radiating from tandem. Upon the seizure of this tandem selector, a. tandem register sender becomes connected thereto and thereafter receives from the local sender over the selected tandem selector a series of impulses which designate both the wanted oilice and the wanted number therein. The tandem register sender thereupon guides the tandem selector to select a. trunk line that connects with 'the wanted oilice (in accordance with the code o! the oiiice registered in the tandem sender) and, at the distant oilice when this trunk line is selected, further guides the local selectors into respective positions to reach the wanted line, whereupon the called subscriber is rung in the usual way and conversation ensues. Upon answer of the called party a signal is relayed back causing the operation of the line message register once. It the conversation lasts longer than a prescribed period, then timing devices in the district selector record the additional charge intervals and operate the line message register as many times as required by the number o! overtime intervals which have elapsed.

It will be noted that the operations above described, which are typical of tandem connections established over panel equipment facilities, are all automatic, that is, the intermediate service of an operator is not required at the tandem omce either to record the details oi the call for billing purposes or to otherwise complete the connections on a manual basis from that point.

In establishing calls on a tandem basis for suburban points, however, straightforward automatic operation controlled bythe subscribers dial are uneconomical in that the charges for the call are diierent from and usually higher than those which are strictly local in character and, also, for the reason that, because of the higher charges, the subscriber is served with an itemized account oi his suburban calls at the time he is billed. In order, therefore, to provide completely automatic service in such cases, it becomes necessary to do automatically what the recording operator does manually; that is, provide automatic recording equipment which is adapted to record, in permanent form, all items of information relating to the connection.

In general, the method of operating my invention is as follows: When the invention is adapted for application to an automatic telephone system of the panel type disclosed in Patent 1,862,549 issued to R.. Raymond and W. J. Scully on June 14, 1932, and in Patent 1,840,132 issued to T. H. Roberts on January 5, 1932, the former patent disclosing the circuits and equipment of a local central oillce having access to trunks leading to a tandem center and the latter patent disclosing the circuits and equipment at the tandem center which are operatively responsive to the extension of a local connection thereto, the subscriber dials a suburban number, the effect oi which is to cause the local sender to direct the district selector to an outgoing or tandem trunk which leads to the tandem switching pillce. Upon the seizure oi said tandem trunk an idle connector circuit is attached thereto. This connector circuit includes registers and pulsing equipment used in common by a, number oi' tandem trunks and associated district selectors, and when it becomes attached to a tandem trunk the local sender transmits thereover to a tandem sender attached to the trunk a plurality of groups of pulses indicative of the wanted line, which pulses are registered in the tandem sender and used for selectively positioning the tandem trunk and a train of other selectors to reach the wanted line. In the connector circuit, electronic devices are provided by means of which the pulses, as they are being transmitted over the trunk, are picked up and registered in a register provided for the purpose, after which they are transmitted into the recording equipment oi thetandem trunk where a permanent record is made of them to indicate the numerical designation of the called line.

Each group of lines terminates on a particular line-iinder frame to which a group of line-finder switches has access, said switches being paired with district selectors that have access to tandem trunks, and this line-finder frame is further provided with a special line-finder switch, herein termed an identifying selector. When the called number designation is disposed of by causing a permanent record of it to be made by the recording device oi the tandem trunk, the connector proceeds to identify the calling line-linder frame and to obtain access to the identifying selector of that frame, to its terminal-engaging brushes and to the up and down drive magnets oi' said selector.

In the connector, a. test relay is connected to each brush of the selector, the selector elevator will be started upward in quest of the calling line while the connector applies a tone potential on the sleeve conductor of the line via the extension thereof in the district selector. The identifying selector, in moving upward, tests all the terminal banks simultaneously and causes the number of terminals passed over, before reaching the terminais o! the calling line, to be counted and registered in the connector. When the terminal marked by the tone is reached, one oi the test relays in the connector will operate to indicate the particular bank of terminals in which the terminal of the calling line appears, the elevator will be stopped while engaged on the terminals to which it was connected when the relay operated. and counting operations will cease when the terminal is reached to which the calling line is connected.

As in the case with making a permanent record of the called line number from the setting of registers in the connector responsive to the transmission of the called pulse code from the local sender to the tandem sender, so too, a permanent record is made of the calling line number from the operation of one of the test relays and the extent of the counting operations in response to the movement of the identifying selector, by causingV the operation of pulsing equipment in response to the operated test relay and in response to the equipment that registered the counting, the former being productive of a number of pulses which indicate the number of the brush used in connecting the identifying selector with the terminal of the calling line and the latter being productive of a number of pulses which indicate the particular terminal, from the bottom of the bank of terminals to which the selected brush has access, to which the tone potential was applied. When the number of terminals in a bank are subdivided into a plurality of groups. which is the most common practice in panel line-finder systems, the counting circuit may be arranged (as it is arranged in the present embodiment of the invention) to register the group of the calling line as a separate item, and then the terminal in the group to which said line is connected. The pulses thus produced are transmitted to the recording equipment associated with the tandem trunk and permanently recorded thereby as the designation c of the called line terminal.

The recording device associated with eachtandem trunk is provided with timing equipment that operates in response to the usual reverse battery signal given over the trunk when the called subscriber answers. Time-spaced impulses are transmitted by this equipment to the recording device as long as the connection is maintained by both subscribers and recorded thereby as a measurement of the duration of the conversation. When either subscriber restores, the timed impulses are stopped.

A clearer conception of the scope and purpose of the invention can be obtained from the iollowing detailed description and appended claims taken in connection with the attached drawings in which:

Fig. l shows a two-party line circuit, the group of linender selectors accessible thereto, and the identifying selector;

Figs. 2, 3 and 4 show the calling lines register of the connector circuit:

Fig. 5 shows the district selector paired with one of the line-finder switches shown in Fig. 1:

Fig. 7 shows the tandem trunk and the recording equipment associated therewith;

Figs. 6 and 8 to 1l, inclusive. show the called line register circuit of the connector; and

Fig. 1A shows the manner in which all of the above-mentioned gures should be arranged with respect t0 each other to disclose the invention completely.

When a long distance call is initiated at either station, say station J or station W of line Ilill, by the removal of the receiver from the switchhook. the line relay IDI is operated over a circuit which extends from battery through the winding of said relay, lower contacts of cut-off relay |02, line conductor |05, over the station loop. back to line conductor |04 to ground on the upper contacts of relay |02. Relay lill operates and closes a current path for a start relay in the line-finder start and control circuit |06 which is fully disclosed in the above-mentioned Raymond-Scully patent. In consequence of the operations in said line-finder start and control circuit, an idle line-finder switch such as, for example, line-finder switch ID3, is caused to operate and hunt for the terminals of the calling line, all in a manner well known to the art and as described in the abovementioned patent. When the line-finder switch engages the terminals of the calling line, which may be assumed to terminate in the terminals of a bank intermediate the 0 bank and the 9th bank, the sequence switch 580 of the district selector 550 is, according to the above-mentioned patent, advanced to position 3 whereupon a link is oper ated to connect the terminals of the district selector to the terminals of an idle local sender. The link and sender, like the line-finder start and control circuit, are likewise disclosed and described in the above-mentioned patent and since they form no part of the present invention except in so far as they cooperate with the circuits of the present invention to cause the selective positioning of a train of selectors to reach the terminals of the wanted line. said link and sender are neither shown nor described herein except by the numeral 560, which designates the sender in conventional block form, the link being disclosed, also conventionally, as a movable connecting medium o intermediate the terminals of the district selector and those of the sender. Reference. however. is made to the above-mentioned Raymond-Scully patent for all circuit operations mentioned herein as taking place in the sender and described in said patent.

Upon the connection of the sender 56B to the district selector, dial tone is transmitted in the well-known manner to the subscribers station from the sender via the district selector and line finder, whereupon the subscriber proceeds to dial the desired number which, in this case and since the call is to be, say. a suburban connection that will be completed through a mechanical tandem office, will comprise one series of digits that designates the wanted ofilce and another series oi' digits that designates the number of the wanted subscriber in that office. When the registration in the sender has proceeded to the point where the district selector 55a may be selectively positioned upon the terminals of an outgoing trunk that terminates at the tandem oiilce, said sender closes the well-known fundamental circuit between it and relay 525 of the district selector by means of which revertive pulses are transmitted to the sender as brushes 55|, 552 and 553 of said selector move into engagement with the terminals of a free outgoing trunk. In this connection, it may be remarked that only such portions of the districi; selector circuit 55|! are disclosed in Fig. 5 as are necessary to a complete understanding oi the invention. this district being identical to the district disclosed in Figs. 1 and 2 of the Raymond- Scully patent above mentioned except for the addition of discharge device 554 and relay 555. For convenience in referring back to said patent for a study oi such parts of the operation oi the district selector as are not covered by the present speciiication and shown in Fig. 5, the last two numerals of the designation of each equipment element and conductor in said ligure have been made to correspond with the last two numerals of the designations of corresponding equipment elements and conductors in Figs. 1 and 2 of said patent. Reference, therefore, is made to such patent for a complete description of the operation of district selector 050 as well as the sender, link and line -iinder start and control circuit as above mentioned.

During all oi the above-mentioned pulsing operations the district selector sequence switch is successively advanced from position 3 to position 10, as described in the above-mentioned Raymond-Scully patent, at which time, with brushes 50|, 052 and 053 positioned upon the terminals of the outgoing trunk to tandem, a circuit is completed for relay 100 in said trunk which extends from battery through the winding of said relay, No. 2 contacts of relay 10|, conductor 00|, brush right springs of cam 004, contacts of relay 031, conductor l, a metallic path in the sender through a contact controlled by the fundamental circuit, conductor IIB, lower springs of cam 000, brush 552, conductor 051, No. 3 contacts oi' relay 10|, to ground.

Relay 100 is individual to the particular tandem trunk herein being used to illustrate the progress oi the call. Other relays shown in Fig. '1 and labeled 100-100" etc. are corresponding relays in other outgoing trunks of the same group. These relays are so arranged that, although more than one may be operated in response to associated trunks to tandem being seized by calling district selectors, yet only one of them will be eilective at a time to seize the connector allotter circuit 000 shown in Fig. 6, as explained hereinafter. Thus when relay 100 operates, it completes a circult from ground over its upper contacts, conductor 100, contacts of slow release relay 00| of the connector allotter 000, brush 002, conductor 000, winding of relay 804 to battery. Relay 60| is a multicontact relay whose armatures are all connected to battery and each of whose make contacts connects to the winding oi' a relay such as relay 605, for example, which, in each connector circuit, is individual to each trunk in the group of trunks extending to the tandem omce. Hence when relay '100 operates, battery is connected to each relay 605 in the connector. However, li' there is more than one relay 100 operated which, as said before, will be the case if more than one tandem trunk is seized at the same time by as many hunting district selectors, only that relay 000 in the connector will operate which is individual to the trunk whose relay 100 is in a certain preferential order with respect to the other relays 1002-100". The reason for this is because the operating circuit of said relay 005 is closed over a series path which extends from ground on the bottom back contacts o! relay 100' of the first trunk in the group, serially through the back contacts oi all the relays of the other trunks in the group, the bottom iront contact of the first operated relay |00 which cuts oil' the chain path to succeeding relays 100, conductor 1i i, left winding of relay B05 to battery on the appropriate pair of contacts oi relay 00|. Obviously if two or more relays 100 happen to be operated at the same time. lt is clear that only one relay 600 in the connector circuit will be operated nothwithstanding the operation oi more than one relay 100. While all the asvoyso relays that will be operated can cause the operation o! relay 004 that connects battery to each of the relays 00B in the connector which, like each of the relays 100 in the group 100'100" are each associated with separate trunks in the group, yet only the circuit oi the relay 005 which is associated with the first operated relay in the group of relays 10W-100" will be closed since the circuit of all other relays G00 will be opened by the back contacts o! the succeeding operated relays in the group of relays 100100".

Relay 005,1n operating, closes its No. 4 contacts and locks to ground thereover on the contacts of relay 000 which is normal Aat this time; over its Nos. 2 and 3 contacts it closes the iilament circuit of electronic devices 000 and B00 whose operations will be described shortly; over its No. l contacts it completes a partial locking circuit for relay GIB; over its Nos. 6 and 1 contacts it connects the grids o! electronic devices 608 and 600 to conductors |51 and 05B, respectively, via. the Nos. 3 and 2 contacts, respectively, of relay 10| and thence into the sender via (on the one side) brush 00|, right. springs o! cam 004, contacts of relay lll to conductor 040 and (on the other side) brush 502, lower springs o! cam 000 to conductor 040: over its No. 8 contacts it completes a partial path for relay 40| via conductor 43B; over its No. 9 contact it closes one point in the path of the winding of the type wheel magnet 102 whose function and operation will be described in the appropriate order; over its No. l0 contacts it completes a circuit to magnet BIB via the brush 031 and the interrupter contacts of said magnet, and in parallei with said magnet at the brush 031, with the winding oi relay 00| causing both said magnet and said relay to operate and step the brushes B02 and 831 of allotter switch B00 to the terminals of a free connector; over its No. 1l contacts it closes a point in the circuit of relay BIB which relay, however, does not operate until relay 40| operates, which occurs at the time when the connector is ready to record the calling line number, as more particularly described hereinafter; while over its No. 5 contacts it completes a circuit for relay 10| which extends from ground on said contacts, conductor 001, winding of relay 10| to battery. The circuits completed above further extend the operation o! the system in the manner noted below.

Relay 10| operates and opens thecircuit of relay 100 which releases, in turn releasing relay B04 which disconnects battery from the operating windings o! all relays 805 without, however, affecting the release of the one relay 605 which has been operated since said relay is locked to the contacts oi' relay 60| as above described; grounds the sleeve terminal through the conductor 658 via the No. 4 contacts and the winding oi' coil 1I0, extends the talking conductors connected to brushes 000 and 051 over its Nos. 2 and 3 front contacts, respectively, to the No. 2 and No. 3 armatures of relay 1H and prepares to lock itself over its own No. 1 contacts to the No. 1 front contacts of relay 1H as explained hereinafter.

The outgoing trunk to tandem is connected to a tandem sender 1I0 of the type shown and described in the above-mentioned patent to T. H. Roberts and when this connection has taken place as therein described, the local sender 560 transmits the called number into said tandem sender H0 by means o! what are known as call indicator pulses, which are groups of tour pulses per digit to set the registers in the tandem sender in accordance with the called number. These pulses are light negative pulses, heavy negative pulses and light positive pulses. There is a switch in the local sender 080 which, upon connection with receiving relays in the tandem send er BIO, rolls through two complete revolutions, during which it produces a set of four pulses per digit, transmitting the same over the line conductors into the tandem sender 1 I Il.

Bridged across the line between relays 1.0i and 1I1 are two conductors, namely 120 and H9 which, through the No. 6 and No. '1 contacts of relay 605 in the connector, extend to the grids of vacuum tubes 60B and B09, respectively, as already described. The anode of tube 608 extends with its positive battery 6 I 2 serially through the lower windings of relays 622, 623 and 624, while the anode of tube 609 extends serially to the same battery through the upper windings of said relays. Relay 624 is a marginal relay and responds only to heavy negative impulses; relay 622 is a negatively polarized relay and responds only to negative pulses while relay 623 is a positively polarized relay and responds only to light positive impulses. As the call indicator pulses are transmitted from local sender 560 to tandem sender 1I0 they affect the grids of vacuum tubes 608 and 809 in a manner to make them conducting when the respective grid biases are altered in response to the presence of negative battery on the assoelated conductors. When either or both tubes operate, one or more of the relays 622, 623 and B24 will operate in the anode circuit of the tube thus affected so that. as the called indicator pulses are transmitted into tandem sender 1I0, they will affect tubes 608 and 609 as well as the relays in their respective anode circuits to record the called number on the registers shown on Figs. 8 and 10.

To illustrate how the called number will be recorded in the registers of the connector, let it be assumed that the called subscribers number is Chelsea 5678. in which event and according to the teachings of the above-mentioned patent to Roberts, eight groups of call indicator pulses in accordance with the following code will be ground on conductor SII over its front contact, No. 3 back contacts oi relay 63e, conductor Sie. No. 3 back contacts o! relay 801, right winding of relay 804 of the tandem digit A register B00 to battery. Relay 804 operates and then locks through its left winding to conductor 84| which is grounded at the No. l contacts of relay 6I3. When the pulse terminates, vacuum tube 608 restores and relays S22 and 624 release. Relay E22, in releasing, removes the shunt around the active winding of relay 634 which now operates in series with its two windings. With relay B34 operated, a circuit is closed for relay 801 extending from battery through the winding oi said relay, No. 2 back contacts of relay 806, conductor 839, No. 2 contacts oi relay 634, conductor BII, back contacts oi relay |036 to ground. Relay 801 operates and locks through the Winding of relay 806, No. 2 contacts of relay 801, conductor 84| to ground, but relay 800 does not operate in this locking circuit inasmuch as it is shunted by the operating ground for relay 801 until relay 634 releases as subsequently described. The next pulse received is alight negative pulse, the quantity of current owing through the anode circuit of tube 608 is correspondingly smaller, and, therefore, relay 622 operates alone whereupon it closes a circuit extending from ground on conductor Ii I I, contacts of relay 622, No. 1 front contacts of relay 634 to the winding of relay 632 over one branch oi the relay network and to the left winding of relay 634 over the other branch of the relay network. Since ground is connected to the other side of the winding of relay B32 via the active winding of relay 634 and the left contacts of relay 632, said relay releases causing thereby relay 634 to hold over its left winding to pulsing ground until the pulse terminates at which time said relay releases and disconnects ground from conductor 839 and thereby removes the shunt around the winding of relay 80E causing said relay to operate in the locking circuit of relay 801. Relays 806 and 801 transfer the circuits controlled by relays 622, 623 and B24 to the tandem digit `B register 0I0. It is apparent that transmitted from local sender 560: 4s

Reg. Sta. Th. Pulses Il il 0 Light negative.. l 2 Light positive... .....do 2 4 Heavy negativeA F. Zi (i ...dO H 4 8 5 l il 3 T 5 8 7 o l. 9 il Lightnegative..

The rst code impulse which, as shown above, is a heavy negative one, causes the operation of tube 608 and, therefore, operation of relays 622 and 624. Relay 622, in operating, connects ground on conductor GII from the back contacts of relay I036, over its front contact. No. l back contacts of relay B34, winding of relay 632, left winding of relay 634 to battery. Relay 632 op erates but relay 634 does not on its left winding in series with relay B32. Furthermore, upon the operation of relay B32 ground is connected over the left contacts of said relay to one side of the right winding of relay 634, ground being connected to its other side by the pulsing ground through the left back contacts of said relay. In consequence of this short circuit of its active winding, relay 634 is prevented from operating at this time. Relay 624, in operating, ,connects only relay 804 has been operated in the tandem digit A register 800 by the group of pulses for the first tandem digit.

During the reception of the rst pulse of the next digit, which is a light negative pulse, relay 522 is operated alone as above described and, ln turn, operates relay B32 in the manner already set forth. At the end of the pulse, relay 634 is operated in series with relay 632 closing thereby a circuit for relay 8H which extends from battery through the winding of relay BII, No. 2 back contacts of relay BIS. No. 2 front contacts of relay 806, conductor l839, No. 2 contacts of relay 634, to grounded conductor 6I I. Relay A8I1 operates and locks through the winding of relay BIB which. in the meanwhile, is held shunted by ground on conductor 84I and ground on conductor 839, the latter being applied to the winding through the No. 2

back contacts of said relay. The second pulse of this digit is a positive pulse and causes the operation of vacuum tube 009 and the consequent operation of relay 623. Relay 023 closes a circuit from ground on conductor 6|| over its front contact, right front contacts of relay 832, conductor 6|4, No. iront contacts of relay 80B, No. 5 back contacts of relay 806, right winding of relay 8I2 to battery. Relay 8|2 operates and then locks through its left winding to grounded conductor 84|. The fourth pulse of the digit which is light negative (the first pulse being assumed to be blank in the place of a positive pulse in its place) causes the operation of relay 022 which releases relay `632. The end of the pulse causes the release of relay 634 as previously described thereby permitting the operation of relay Elli in the locking circuit of relay 0|1. The pulse group of the second tandem digit has resulted in the operation and locking of relay lIl I 2 of register Il I 0.

'I'he first pulse of the third tandem digit is a positive pulse. A circuit therefore is closed which extends from ground at the contact of relay B23 via conductor 8| I, right back contacts of relay 632 which has not been operated as yet, conductor 6|5, No. 1 front contacts of relays 801 and 0|1, No. l back contacts of relay `ll21, right winding of relay 82| to battery. Relay 82| operates and then locks through its left winding to ground on conductor 94|. The second pulse, which is a heavy negative pulse, causes the operation of relays 622 and 024 as previously described. Relay 624 closes a circuit from grounded conductor EH through its own contacts, No. 3 back contacts of relay B34, conductor 6|0, No. 3 front contacts of relays `801 and 8|1, No. 3 back contacts of relay 821, the right winding of relay 824 to battery. Relay 824 operates and then locks to ground on conductor 84|. 'Ihe operation of relay 622, in response to this pulse and to the following light negative pulse, causes the operation and release of relays 632 and 634 and thereby brings about the operation and locking of relays l026 and 821 in the same manner as the previous two sets of steering relays 806 and 801, and 8|'0 and 9|1. Relays 02| and 024 are` therefore, operated in the tandem C register 820 to record the designation of the letter E of the called subscriber's number.

Assuming that the called subscribers number includes no stations digit, the pulse code of the next digit received will consist of two light pulses which are the equivalent of the digit zero. No register relay in the ten thousands or stations register 830 will be operated, but the steering relays 836 and 831 will be operated in response to the operation of relay 622, to advance the circuit to the next or thousand's digit register |000.

The remaining digits are recorded in a similar manner on registers |000, IOI0, |020 and |030 and result in the operation and locking of relays |003 and |004 in the thousands register |000, relays |0|| and |0|3 in the hundreds register |0I0, relays |024 and |023 in the tens register |020 and relays |03|, |033 and |034 in the units register |030. Any other number will be recorded in the above registers in accordance with the abovementioned pulse code.

For purposes of closing through a two-wire odice selector (not shown) which may sometimes be included in the train of selectors extending between the calling and the called oiiices, the local sender 560 is adapted to transmit, after the numerical pulse code, a heavy positive pulse, to cause the operation of a polarized relay in said two-wire selector as a signal to prepare the talking conductors therein for the transmission of conversation thereover. Such a pulse would cause the activation of vacuum tube B09 and the operation of the marginal pulse relay 624 and the p0sitive polarized relay 623. However, since ground on conductor 4(ill is applied to the armature of these relays through the back contact of relay |036 which is operated at the time relays E23 and '024 operate in response to the transmission of the heavy positive pulse, their operation will have no effect". Following the transmission of the nal heavy pulse, the sender 560 is disconnected from the district selector 550 in the manner described in the above-mentioned Raymond-Scully patent.

As each digit of the called number is recorded in each oi the separate registers 000, 0|0, 820, etc., it is immediately caused to be printed upon a tape controlled by the recording mechanism 130 which constitutes a part of the outgoing trunk and which may be of any suitable type. The recording operations are controlled by the rotary switches 000, 9|0, etc., |I00, |||0, etc., which are associated respectively with registers $00, 0|0, etc., |000. IOI0, etc. Hence when the register 000 has been operated to register the pulse code of the letter C of the ofIlce name, a circuit is completed for relay 906 which extends from ground on the No. l contacts of relay 806, No. l contacts of relay B08, conductor 900, winding of relay 906, conductor sus, brush els of switch 64o and the r11-st terminal accessible thereto, to battery. Relay 906 operas and closes its contact by which the ground on conductor 908 is applied to the winding of the stepping magnet 90| of switch 900 through the interrupter contacts of said magnet. Magnet 90| operates and steps the switch brushes 902 to 905, inclusive, one terminal whereupon a circuit is completed for the winding of the type wheel magnet 102 of the recording equipment, said circuit extending from ground on brush 902, conductor 901, No. 3 contacts of relay EIB, No. 9 contacts of relay 605, conductor 6|9, winding of type Wheel magnet 102 to battery. The magnet operates, closes an obvious circuit for slow-to-release relay 103 and advances the type wheel 104 one notch to register one pulse. When stepping magnet 90| operates it, of course, breaks the operating circuit through its own interrupter contacts whereupon the magnet releases and advances the brushes of switch 900 to the next or third terminal. Now if the rst digit registered in register B00 is a zero, which means that no relays in the register are operated, then with brush 903 on the zero terminal (so labelled), a circuit will be completed for relay B08 which extends from battery through the winding of said relay, conductor 809, brush 903 and zero terminal of its arc, conductor 9|8, No. 4 back contacts of relay No. 3 back contacts of relay 002, No. 4 back contacts of relay B03, No. 2 back contacts of relay 804, No. 1 contacts of relay 80E to ground, However, since, in illustrating the establishment of the connection, it has been assumed that the first number of the digit registered in register 800 is that corresponding to the letter C and hence in the pulse code as given correspending to digit 2, no such circuit will be completed for relay 808 which means that the circuit for relay 306 is still effective so that, upon the release oi.' stepping magnet 90| at which time the brushes of the switch 900 are advanced another terminal, the circuit of said magnet is completed once more over the previously described path and the brushes 902 to 905 are therefore advanced to the next terminal. In this position of the brushes, brush 002 will be in contact with terminal 4 of its arc, the previously described circuit for magnet 102 is again completed whereupon said magnet again operates to advance the wheel 104 another notch to record a second pulse. The operation oi magnet 102 again closes the obvious circuit for relay 103, which relay is maintained in an operated position between pulses due to its slow-to-release characteristics, and, upon the advance of switch 900 by the release of its magnet 90| as previously described, magnet 102 releases. Since relay 103 is in an operated position atY this time, a circuit is completed for the printing and advance magnet 105, which circuit extends from battery through the winding of said magnet. contacts of relay 103, normal contacts of magnet 102 to ground. The printing magnet operates and causes the printing of the second pulse upon the tape.

With switch 900 in position 4 and with the digit 2 registered in register 000, as is evidenced by the operated condition of relay 800, switch 000 transmits another pulse to magnet 102 which is then recorded by the operation of magnet 105, advances its brushes to the next terminals beyond which brush 902 transmitted the third pulse, and a circuit is then completed for relay 008 which extends from battery through the winding of said relay. conductor 009, brush 903, and terminal 2 lso designated) on the arc accessible thereto, conductor 9I'I, No. 3 back contacts of relay 803, No. 2 normally made contacts of relay 80|. No. 2 front contacts of relay 804, to ground on the No. 1 front contacts of relay 806. Relay 000 operates, opens the circuit of relay 906 and completes that of relay 62| and magnet 625 of switch 640, which circuit extends from ground on the No, 2 front contacts of relay 008, conductor SI5, No. 4 back contacts of relay 6|3, normal terminal and brush SI1, winding of relay 62| to battery and, in parallel therewith over the back contact of said relay, to the winding of magnet 625 of the stepping switch 640. Switch 640 is of the forward stroke type, well known in the signaling arts, and advances its brushes upon the operation of its driving magnet (as contrasted with the switch 000, for example, which is of the back stroke type and advances its brushes in the release of its driving magnet) so that, when magnet 025 operates, it causes brushes BIG and BII to step from the first terminal to the second terminal of their respective cooperating arcs, whereupon the circuit for relay 62| is broken, that of the magnet 525 having been broken previously at the contacts of said relay,

and thereby causing said relay to release. Relay 02| releases and since magnet 625 is already released, brushes BIG and SI1 remain upon the terminals, to which they have been stepped. With the brushes of switch 040 on terminal 2 of their respective arcs, the circuit is ready for causing the printing of the pulses of the second digit of the called ofce name if the same have been registered in register BIO. If, by the time the pulses of the rst digit have been recorded upon the tape, the second digit has not yet been received from the sender, the connector will wait until said digit is registered in register 8|0, which registration will then be evidenced by the operation of relays HIB and 8l1, at which time a circuit is completed for relay 9 I 6 which extends from ground on the No. l contact of relay 8IE, No. l contact of relay 8I0, conductor 9|9, winding of relay BIB, conductor 921, brush SI and second terminal upon which it is standing, to battery. Relay 0| 6 operates in said circuit and applies operating ground through its own contacts and the interrupter contacts of the stepping magnet 9| I of switch 9|0 to form a complete circuit through the winding oi said magnet. to battery. Magnet 0H operates and steps the brushes 0I! to SI5, inclusive, from their respec tive first terminals to their respective second terminals, in which positions a ground pulse is transmitted to the magnet 102 over a circuit which extends from ground on the second terminal of the arc associated with brush SH2, and thence as previously traced to the winding of magnet 102. caus ing said magnet to advance the type wheel the equivalent of one pulse. The magnet operates, closes its contacts and, as before, causes the operation of relay 103. Upon the release of said magnet 102, the previously traced circuit of the recording magnet 105 is completed, said magnet is operated and a pulse mark is made upon the tape. In the same manner as described for the transmission of the pulse corresponding to the first digit as recorded in register 800, an equivalent number of pulses will be transmitted by brush 0 I 2 to the magnet 102 for the advance of the type wheel 104 an appropriate number of pulse spaces (four spaces) corresponding to the letter H and the consequent operation of recording magnet 105, as described, an equal number of times (four times) to record that many pulses on the tape.

When the pulses for the letter H have been transmitted to magnet 102, a circuit is completed for relay 0| 8 which is traced from battery through the winding oi said relay. conductor 920, brush Si 3 and cooperating terminal No. 4, conductor 929, No. 3 front contacts of relay 8I2, No. 4 back contacts of relay 8|3, No. 2 back contacts of relay 0 I 4, to ground on the No. 1 front contacts of relay 8|0. Relay BIB operates and performs the same functions for switch 9|0 which was performed by relay 808 for switch 900; that is, it opens the circuit of relay SIB and completes that of stepping magnet 625 and relay 62| over the No. 2 terminal to which brush 6 I 1 is now connected, causing said magnet and said relay to operate and step the brushes BIG and BI'I of said switch to the third terminal, respectively, in which positions the connector is ready to transmit the pulses corresponding to the third digit of the office name as recorded on register 820 if the same has been received from the sender.

It is not believed necessary to detail the operation of each one of the remaining switches 020. 030, Illlll, |||0, etc., as they operate to cause the recording on the tape controlled by magnets 102 and '|05 of the required number of pulses corresponding to each of the digits of the called number, as all operations are identical with those already described except for the fact that the brushes of each of the switches will be stepped, in pulsing, to the terminals which correspond to the number of pulses recorded in the correlated register of Figs. 8 and 10 and will remain there until the last or units pulses of the called number are recorded upon the tape, at which time relay |03B is caused to operate over a circuit extending from battery through the winding of said relay, brush H33 and terminal No. 8 of the arc, conductor i |01,No. 2 front contacts of relay |033, No. 2 front contacts of relay |03 I, No. 2 front contacts or" relay |034 to ground on the No. 1 front contacts of relay |036. Relay |038 operates, breaks the circuit of relay l |36 and completes that of relay 62| and magnet 825, said circuit being traced from ground over the No. 2 front contacts of relay |030, conductor I I I1, brush 6|1 and cooperating terminal, winding of relay 62| and, in parallel therewith over the back contacts of said relay, to the winding of stepping magnet 625 to battery. Switch 040 steps in consequence of the operation of magnet 025 and brushes BIB and M1 are advanced to their ilrst terminal. Relay |030 also completes another circuit which extends from ground through the No. 3 contacts of said relay, conductor HiB, winding oi relay 5|3 to battery. Relay 6|3 operates and locks over its No. 2 contacts to ground on the No. l contacts of relay 605, disconnects ground from conductor 04| thereby causing the locked relays in the registers of Figs. 8 and 10 to unlock and release. including relays 80B, BIB, etc., and |008, |0|8, etc., breaks the path to the magnet 102, further opens a set of contacts in the path of relay 02| and magnet 525, and further connects ground over its No. 5 contacts to conductor 542, Inasmuch as al1 the switches shown in Figs. 9 and ll are not normal because of the different setting taken by each of them when transmitting the pulses of the called number to the magnet 102, brushes 904, 9|4, etc., and H04, |||4, etc., will be on the commoned portion of their respective arcs whereupon, upon the release of relays B, 0|8, etc., and |008, i0|0, etc., separate driving circuits are completed to the winding of the magnet of each of the switches 50B-930 and I|00| |30 whereby the brushes of said switches are returned to their respective normal terminals. For instance, and by way of illustrating all of the above circuits, when relay 008 releases, a self-interrupted drive circuit is completed for magnet 90| of switch 900 which extends from ground on the No. 2 back contacts of relay 808, conductor 939, brush 904 and the commoned terminals accessible thereto, interrupter contacts of stepping magnet 90| to battery. Magnet 00| operates on self-interruptions and drives the brushes of switch 900 back to their respective normal terminals.- In the same way, upon the release of relays Bill-830 and |008-I03B as above enumerated, the brushes of the corresponding switches 9i0-030 and ||00| |30 are restored to normal. When all of these switches are normal, a circuit is completed from ground on the No. contacts of relay M3, conductor 642, serially through the brushes H35, H25, etc., and 935, 925, etc., conductor 938, winding of relay 520 to battery, causing said relay to operate.

With the recording of the pulses that designate the number of the called ofl'lce name and number on the tape controlled by magnets 102 and 105 associated with the outgoing tandem trunk, the connector, if not otherwise engaged, is now ready to record the designation of the calling line. Each connector circuit, besides having one relay |505 for each outgoing trunk of a group, also has a relay 40| for each outgoing trunk of a group. Since all distict selectors are divided into groups available to different line groups, it is also provided with a relay 4|5 for each of these selector groups. Hence, with the operation of relay 626, circuit operations are begun by which the connector is caused to determine the calling line designation by rst energizing the relay 40| in the connector belonging to the outgoing trunk of the connection and then operating the group relay 4|5 marking the district selector group containing the selector connected to said trunk. Therefore, when relay 626 operates, a circuit is completed for relay 40| which is traced from ground on the contacts of relay 620, contacts of relay 621, No. 8 contacts of relay 005, conductor 43B, winding of relay 40| to battery. Should any other relay 40| of any group be in an operated condition, which indicates that the connector is then occupied with the district selector connected to the trunk marked by said other relay in receiving the caillng line number of the line connected to the lineflnder end o! said district selector, relay 021 will be operated over common conductor 402 from ground on the No. 10 contacts of said operated relay 40|, in consequence of which the circuit just described for the operation of relay 40| 0I the outgoing trunk shown in Fig. 7 will not be closed. On the other hand, if, when the connector is finished with its operations of recording the called line designation over one trunk and is not otherwise engaged in determining the calling line designation over another trunk, relay 621 will be released which is the signal that the connector is free to determine the calling line designation over the iirst trunk, commencing operations to do so by the operation of relay 40| of said trunk as above described. Relay 40| operates and then locks over its No. 3 contacts, conductor 404 to ground on the contacts of relay lill. Relay 40| operated, applies ground to its No. 4 contacts and completes a circuit over conductor 403, No. 1l contacts o! relay 505, winding ci' relay BHI to battery. Relay Gili operates and closes an obvious circuit for relay 606 which, in operating, unlocks relay 605. Upon the release, of relayll. relays BIB and 606 release and since relay 6I! is locked to the No. 1 contacts of relay 605, relay 6|3 also releases, thus restoring to normal that part of the connector which handles the registering and recording of the called line number.

As already noted, the operation of relay 40| followed the operation of relay 526. Since, according to the above-mentioned Raymond-Scully patent, the district selector is in position |5 after the pulses of the called line number have been transmitted into the tandem sender 1|0, relay 405 is placed across the tip and ring conductors of the partly established connection with its battery and ground connection poled against district polarized supervisory relay 533. The circuit path is as follows: battery through the upper winding of relay 405, No. 1 back contacts of relay 406, No. l back contacts of relay 401, conductor 400, No. 6 contacts of relay 40|, conductor 1|9. No. 2 front contact of relay 10|, conductor 550, brush 55|, upper right and lower left springs oi' cam 504, right upper winding of repeat coil 532, lett contacts of cam 503, winding oi' relay 533, right lower winding of repeat coil 532, left springs oi' cam 505, brush 552, conductor 551, No. 3 front contacts of relay 10|, conductor 120, No. 7 contaets oi relay 40|, conductor 408, No. 2 contacts of relay 401, No. 2 back contacts of relay 400. lower winding of relay 405 to ground. Relay 400 operates in this circuit but relay 533 does not. Relay 405, upon operating, operates relay 4|0 over an obvious circuit and then locks over its No. 2 contacts to ground on the No. 3 contacts of relay 401.

The function of relay 4|0 is to summon the simplex allotter 520, of which there is one iurnished per office and which has accessibility to all connectors. The simplex allotter causes the connector it acts upon to send a simplex signal over the trunk conductors for the purpose of getting the district selector attached to the outgoing trunk to operate that relay 4 I 5 in the connector that marks the group of district selectors i and line iinders) of which the district selector attached to the outgoing trunk in Fig. 7 is one. Issuing of the simplex signal, however, is held up until the district selector is in a position to act upon it, which is position l5 of its sequence switch 500, in order to reduce allotter holding time, and to make the signal as readily available as possible to other connectors. One allotter is provided and one simplex signal is transmitted at a time because, if two connectors are sending simplex signals simultaneously they each would receive both group indications. Hence when relay 4|0 operates, it completes a circuit for relay 62s of the allotter, which circuit is traced from ground through its No. 1 contacts, conductor 4I I, resistance 629, winding of relay 628 to battery. Relay 62B operates and completes a self-interrupting circuit for the stepping magnet 63| from ground on its contacts, No. 3 contacts of relay E33, interrupter contacts of magnet 63|, winding of said magnet to battery. Magnet 63| operates under self-interruptions until brush 638 of the allotter switch 630 engages that terminal of its arc which has ground applied thereto by relay 4I0 when an obvious circuit is then completed for relay 633 which, by opening its No. 3 contacts upon operation, arrests further operations of the magnet 63| and thereby causes brushes B38, 635 and 639 to come to a stop upon the terminals thus selected.

Relay 633. upon operating, further compietes a circuit for relay 4|2 that extends from ground on the No. l contacts of said relay 633, brush 539, conductor 4|3, winding of relay 4|2 to battery, and another circuit for relay 4046 which extends from ground through its No. 2 contacts, brush 635, conductor 4|4, winding ofrelay 406 to battery. Relay 4|2, which has a pair of contacts for each group relay 4|5, operates and applies ground to the winding of each of said relays while relay 406, upon operating, disconnects relay 405 from the trunk conductors and connects battery to both of said conductors via resistances 426 and 421, re spectivcly, to form a simplex circuit over a path already traced which includes relay 533. In parallel with the winding of relay 533, is one clement of a two-element gas-filled tube 554 to the other element of which is connected the winding of relay 555, the other terminal of the winding of said relay extending to ground. The potential on the tube, as established by the application of battery to the two trunk conductors via resistances 426 and 421, is such that the tube breaks down and becomes conducting whereupon current will flow through it and through the winding of relay 555 thus causing it to operate. Since the sequence switch 500 is in position 15, a circuit is now completed for relay 4I5 of the group of district selectors which includes the district selector over which the call is beng established, said circuit extending from battery through resistance 556, springs of cam 564, conductor 56|, winding of relay 4|5 to ground on a pair of contacts on relay 4I2, causing said relay 4|5 to operate.

Relay 4I5, upon operating, closes an obvious circuit for relay 422 which operates thereover and locks over its No. i3 contacts to ground on conductor 404, and another circuit for relay 4|5 which extends from ground over its upper contacts, No. 3 contacts of relay 4|1, winding of relay 4|6 to battery. Relay 4|6 operates and locks in series with the winding of relay 4|1, its own No, 2 contacts, to ground on conductor 404; Relay 4|`|. however. does not operate at this time, it being held shunted by the ground over the upper contacts of relay 4|5 applied to the other side of its winding.

As there is one relay 4|5 in the connector for every district line-finder group to which the connector has access. so there is, in the connector,

one relay 422 for every such group, each relay 4 I 5 for one such group operating a corresponding relay 422 as above described for that group. NowV the function of relay 422 is to extend into the connector the ten brushes of the line-identifying selector ||0 which is located on the same frame as the line-finder switches of the district lineiinder group that serves the main group of lines in which the calling line is included. The identiying selector I|0 is of the same construction as the individual line-finder switches except that each of its ten brushes is adapted to engage but one terminal of each terminal set engaged thereby in the smaller subdivisions of the main group of lines served by the line-finder switches of the group. In the most general practice, line-nder frames of the type contemplated by this invention are of the so-called panel type and accommodate four hundred lines which are divided into smaller groups of forty lines, each accessible to one set of brushes of a line-nder switch, the group of such switches serving the four hundred lines being determined, of course, by the tramo density. One identifying selector I I0 is thus used for one group of such line-lnder switches, and the function of this selector, when seized by the connector, is to locate the sleeve terminal of the calling line which, considering that the entire main group of four hundred lines is subdivided into ten smaller groups of forty lines each, may be located in any one of the ten groups. Each brush |40- |49 of the identifying selector |I0 is joined by a conductor IZB-|29 to a brush of a commutator segment which, in turn, is joined by a conductor to one of the armature contacts of Nos. l to 10, inclusive, of the contact sets of relay 422 in each of the connectors. There is also provided, for the identifying selector III), one ground commutator |08 and a pulsing commutator |01 the latter of which has forty segments in it, one for each line in a group of forty, with which a brush |09 cooperates to provide, in conjunction with brush iII, interrupted ground from commutator |08 to the conductor |I2 connected to commutator |01, which conductor is connected to the armature of the No. 12 contact set of relay 422.

When relay 4|6 operated, it not only locked itself up in series with the winding of relay 4I1, as already described, but, over its No. l contacts. it further completed a circuit for relay 'I I I of the outgoing trunk, which circuit is traced from ground on said contacts, No. 2 contacts of relay 40|, conductor 4I8, winding of relay 'H1 to battery. Relay 1|1 operates, disconnects the forward end of the trunk from the terminals thereof on the district selector frame and connects said terminals to the left windings of repeating coil 126 and its associated relay 1|4, the path for` which is traced from conductor 556, No. 2 front contacts of relay 10|, No. 2 front contacts of relay 1|1, left upper winding of repeat coil 12B, upper winding of relay 'H4 to ground; and from battery through the lower Winding of said relay. left lower winding of repeat coil 1246, No. 3 front contacts of relay 1I'I, No. 3 front contacts of re lay 10| to conductor 551. On the district selector side, this path is joined to that already traced for relay 553 and since the current ilowing through the joined paths is in a direction to operate relay 533, said relay operates and advances the district sequence switch 500 to position 16 as described in the above-mentioned Raymond- Scully patent. In this position, as will be described shortly. the connector transmits a tone current over the sleeve of the district selector

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