US2104449A

US2104449A - Telephone system

Info

Publication number: US2104449A
Application number: US95530A
Authority: US
Inventors: Langford J Bowne; Beach Howard; Frederick R Lamberty
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1936-08-12
Filing date: 1936-08-12
Publication date: 1938-01-04
Anticipated expiration: 1955-01-04

Description

Jan. 4, 1938.

Y F/G. Z

L. J. BoWNE Er AL 2,104,449

TELEPHONE SYSTEM Filed Aug. 12, 193e 14 sheets-snee?. 1

CALL/NG 5 LINK ATTORNEY Jan. 4, l J. BOWNE E]- AL TELEPHONE SYSTEM Filed Aug. l2, 1936 14 Sheets-Sheet 2 A T TORNEY Jan, 4, L. J. BQWNE Er AL TELEPHONE SYSTEM Filed Aug. 142, 193e 14 sheetsheef. 3

A T Tom/Ey Jan. 4, 1938. L. .1. BowNE Er AL TELEPHONE SYSTEM Filed Aug. l2, 1936 14 Sheets-Sheet 4 Jam 4, 1938- 1 .1. BowNE Er AL 2,104,449'

TELEPHONE SYSTEM V Filed Aug. 12, 193e' 14 sheets-sheet 5 BY WWW AT TOR/VEV Jan. 4, 193s. L J, BOWNE ET AL 2,104,449

TELEPHONE SYSTEM Filed Aug. l2, 1956 14 Sheets-Sheet 6 ONE PER LINK SECOND LINK ik i5 u: ws gl ons Fen anal/P om PE@ sua-snow ons PER 0F mun/rs oF TEN L//ves oFF/c5 CONTROL 7C CIRCUIT A TTORNEV Jan. 4, L, J. BOWNE ET AL TELEPHONE SYSTEM Filed Aug. l2, 1936 14 Sheets-Sheet 7 .By A AT OPA/EY Jan 4, V |-l J' BOWNE ET AL TELEPHONE SYSTEM Filed Aug. l2, 1936 14 Sheets-Sheet 8 k o u .9v V ATT RNB Jan. 4, 1938. J, BOWNE ALY 2,104,449

TELEPHONE SYSTEM Filed Aug. 12, 19:56 14 SmaetS--sheml 9 5y Afro@ Eg Jan. 4, 1938. L.. J. BowNE ET AL 2,104,449

TELEPHONE SYSTEM Filed Aug. 12, 1956 14 Sheets-Shea? l0 Br MMM- ATTO NEV Jan. 4, 1938. n l L. .1.v BowNE ALr 12,104,449v

TELEPHONE SYSTEM v Filed Aug.12, 1936 14sheefs-sheeff11 ay MW A T TORNEI l Jan. 4, l J BCWNE E-l- AL TELEPHONE SYSTEM l Filed Aug. 12, 1936 14 sheets-sheet 12 By www A T TORNEV Jan. 4, L' Jp BOWNE E1- AL TELEPHONE SYSTEM Filed Aug. 12, 1936 14 Sheets-Sheet 13 J. BowNE Er AL TELEPHONE SYSTEM Jan. 4, 1938.

Filed Aug. 12',` 1936 T0 CONTINUOUS RING/NG 14 Sheets-Sheet 14 A T TORNE Y Patented Jan. 4, 1938 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Langford J. Bowne, Howard Beach, Frederick R. Lamberty, Brooklyn, N. Y., and Ray L. Stokely, deceased, late of Floral Fark, N. Y., by Grace MacDonald Stokely, executrix, Floral Park, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application August 12, 1936, Serial No. 95,530

19 Claims.

l subscribers line to another over a cross-bar switch through a link circuit and in which the removal of a calling subscribers receiver from the switchhook causes the calling line to be connected to one branch of a link circuit through the switch and the dialing of a called subscribers number causes the called subscribers line to be connected to the other branch of said link through the switch. A system of this type is disclosed in the patent to L. R. Waller 1,567,309 of December 29, 1925. Systems have also been provided in which in addition to connections between subscribers lines, connections may also beextended from a subscriber's line to a trunk. A system of this type is disclosed in the patent to E. E. Hinrichsen 1,567,365 of December 29, 1925.

A feature oi the present invention is an ar- A rangement in a system of this general character in which a common control circuit is used for determining the progress of a call through the switch. This control circuit is seized when the calling subscriber removes his receiver from the switchhook and released when the calling line is connected to the link and again seized when the dialing of the called subscribers number is completed and again released a short time thereaft-er. The release of the common control circuit the first time is controlled by the operation of a relay operated over a sleeve circuit established when a connection between the calling subscribers line and the link is completed. The release of the control circuit the second time is controlled by the operation of another relay in.

case the called line is found idle and by the operation of a third relay in case the called line is busy on a call made to a subscriber of another line or on a call made to a called subscriber on the same line as the calling subscriber due to the busy condition of this line.

Another feature is an arrangement in which connections may be established for tandem calls,

that is, for a call incoming to the system over one trunk from a distant oilice and outgoingover another trunk to some other distant ofiice. In this arrangement a special tandem cross-bar switch may be used exclusively for the establishing of tandem connections between trunks and to aid in the establishing of such through connections, temporary use is made of an idle link in the regular trunk and link connecting cross.,

bar switch. y

In the system embodying the features of this invention, certain lines terminating therein have two conductors while others have butja single grounded conductor. In order to terminatethe single-conductor lines with two conductorrsjin'the cross-bar switch in the same manner as the twoconductor lines, repeating coils are employed. 'I'he single conductor of a line is connected through the windings of one side of the repeating coil to ground and the windings of the other side of the repeating coil are connected in series to two conductors terminating in the cross-bar switch. It is a feature of the present invention to provide means for entirely eliminating the repeating coil from a single-conductor line when ringing out over such a line. When the ringing relay in the system is operated to apply ringing current it causes, over a special lead, the operation of a relay in the single-conductor line circuit. 'I'his relay disconnects the single conductor from the windings of the repeating coil and connects it to a ringing current source. This relay also opens an alternating current connection between the two windings of the other side of repeating coil and prevents a direct current connection from being closed between these windings. Thus, while the ringing relay connects the two conductors for the single-conductor line to a ringing current source, no ringing current can pass over these two conductors through the repeating coil and consequently cause no unnecessary drain on the ringing current source.

Another feature of the invention relates to the means for operating two sets of relays of the control circuit employed during the extension of a connection. One relay operates in each of these sets to mark a calling line and another relay in one of said sets operates to mark the link used in the establishing of a connection. This means comprises two chain circuits for each set of relays with a fuse connected between each chain circuit and a single source of current. Each chain circuit of a pair is capable of operating said relays independently of the other but normally both chain circuits operate the relays. The chain circuits are so arranged with other relay combinations in the control circuit, that when a relay in a set is operated, the relays in said set located between said operated relay and the source of current are made inoperative while the remaining relays in the set are made ineffective in controlling the establishing of other connections during the establishing ol' the connection controlled by the operated relay.

Referring now to the drawings, Fig. 1 shows in diagrammatic form the arrangement in a small exchange of subscribers lines and trunks in the system einbodying'the applicants invention.

Fig. 2 shows the arrangement ofthe succeeding Figures 3 to 1'7 for the reading of the drawings. These Figures 3 to 17 show a complete system embodying the applicants invention. Figs. 3 and 4 show two types of subscribers lines. shows the cross-bar switches and their selecting and holding magnets used in this system. Figs. 6 and '7 show various details of a. trunk circuit. Fig. 8 shows an allotter circuit for link circuits. Figs..9, 10 and 11 show'a common control circuit. Figs. 12, 13, 14 and 15 show the details of a link circuit used for establishing a connection between lines or trunks. Figs. 16 and 17 show the details of a ringing equipment, tone, timing and alarm signal circuits required in this system.

Referring now particularly to Fig. 1, connections may` be established between subscribers lines A and B through the cross-bar switch C over a link in group D serving the switch C. The connection established from the calling line A by the seizure of one end of an allotted link and the subscriber of the calling line then dials for the desired subscribers line and operates switch C to connect the desired line to the other end of` this link. Cross-bar switches of any well-known type may be used in which thev operation of a horizontal and a vertical bar causes a connection between circuit contacts at the intersecting point. Connections may be made from a subscribers line to a trunk E or F outgoing from the exchange or from a trunk E or F to a subscriber in the exchange and may be established in the same manner as between the two subscribers lines, While a tandem connection may be made through the exchange from, for example, trunk E to trunk F through the cross-bar switch G. In this case the switch C and a link circuitare 4temporarily used during the establishing of the connection which is then transferred to -switch G. Calls such as outlined above will now be traced in detail in the following description in connection with Figs. 3 to 17.

The first connection that will be described is from the subscriber of the line A to the subscriber of the line B in the exchange.` The line A is a grounded return single-conductor line and the subscribers set has been shown merely by a circle. When the subscriber of this line removes the receiver from the switchhock a circuit is completed for the operation of relay |90 from battery, winding of this relay, lower left-hand winding of repeating coil |0|, contacts of relay |03,

Fig. 5

upper winding of retardation coll 00 to the subscribers set to ground. This causes the operation of relay |00 which closes a connection over the tip and ring conductors of the line for the line relay 500 from battery, left-hand winding of this relay, contacts of the holding magnet 50|, ring conductor, the upper right-hand winding of the repeating coil contacts of relay |00, lower right-hand winding of the repeating coil |0|, the tip conductor, right-hand winding of the line relay 500, contacts of holding magnet to ground. The line relay 500 closes a connection to ground for the GRP and LT leads. It should be observed that the relay 500 closes a, circuit for relay |005 over lead LT when relay H00 is operated as hereinafter described, from battery, make-beforebreak contacts of relays |0|3, |0|2 and |005, windings of relay |005, contacts of relay H00, lead LT, contacts of relays 502 and 500 to ground.

This relay |005 represents the first subscriber in l.

a group, that is in this case, the subscriber of line A, to the control circuit in Fig. 9. The ground on the GRP lead causes the operation of relay 900 from battery make-before-break contacts of relays 90| and 902, contacts of relay 903, Windings of relay 900, make-before-break contacts of relay 904 to the GRP lead, contacts of relay 502 to groundvat contacts of line relay 500. It should be observed at this time that in the part of the control circuit shown in Fig. 9 a number of sets 1' of group relays are shown, of which relaysl90| and 905 are provided for a link (not shown) relays 902 and 906 are provided for the rst link shown in detail in Figs. 12 to 15, relay 903 is provided for the whole exchange, relays 900 and 904 are provided for the particular group of ten lines in which the calling line is located and relays 901 and 908 are provided for a particular group of trunks. Other relays may be supplied in the connections between

relays

900 and 904 on the one hand, and relays 901 and 908 on the other hand for additional group relay sets for other groups of lines and trunks, and between relays 902 and 905 on the one hand and relays 90| and 905 on the other hand for additional lrelay sets for other links.

Relay 900 is locked from battery through its windings and its inner upper and lower armatures and contacts over lead GRP to the ground at line relay 500 independent of the battery at the make-before-break contacts of relay 90|. Relay 904 now operates from battery, windings of this relay, outer upper and lower armatures and front contacts of relay 900 through intermediate relays (not shown), outer upper and lower armatures and contacts of relay 901, make-before-break contacts of relay 903, inner left-hand and right-hand armatures of back contacts of relay |000 to ground in Fig. `10. Relay 900 in operating also disconnects ground from the armatures of the group relays towards the right such as 905 and 906 and other associ.- ated corresponding relays and'disconnects battey from the armatures of the group relays to- Wardsrthe left such as relays 901 and other relays of that kind so as to prevent any of these relays from becoming effective while the control circuit is engaged in this call due to the operation of

relays

900 and 904. If a relay such as 902 operates it is ineffective as the associated relay 905 cannot operate as the ground is disconnected by relay 900 and a relay such as 901 cannot operate as the battery is disconnected by relay 999. The operation of the relay 904 provided a path for locking the relay 900 independently of the ground on the GRP lead, the locking circuit extending from battery, the operated 4armatures and front contacts of relay 900 `and its windings, upper and lower inner armatures and front contacts of relay 004, contacts of relay to ground.

In Fig. 11 there is a relay H00, which is provided for the particular group of subscribers" lines in which the calling line A is located and similar relays are provided for other groups but not shown. It may be mentioned here that there is also one similar relay provided for each group of trunks, only one of which has been shown. This relay is numbered |0| and represents the group of. trunks of which the trunk shown in Figs. 6 and 7 is one. Upon the operation ci relay 904 the circuit is completed for the relay H00 from battery, winding of this relay, contacts of relay 004 to gro-und. It should also be observed that in the allotter circuit shown in Fig. 8 there is one relay provided for each link, relay 800 for the rst link, 00| for the second, 802 for the third and 803 for the fourth link, this circuit If the alcircuit being provided with only four links. lotter circuit is normal and the first link which has been shown in Figs. 12 to 15 is idle relay 800 is operated and maintained operated over a locking circuit from battery, its left-hand winding, inner left-hand armature and front contact, left-hand make-before-break contacts of relays 80|, 802 and 803, right-hand winding of relay 805 to ground and another locking winding from battery at the third outer right-hand armature and back contact of relay 805, inner right-hand armature and back contact of relay 801, right-hand winding of relay 800, inner right hand armature and front contact of this relay, right-hand make-before-break contacts of relays 80|, 802 and 803. left-hand winding of relay 809 to ground. Relays 805 and 800 are therefore also operated at this time. As soon as relay 904 operated a circuit was closed for the operation of a start relay |003 in the control circuit from battery, windings of this relay, contacts of relays |000, 904, 8|0 and 801 to ground. Relay |003 provides a locking circuit over its left-hand winding, contacts of relay |000, and its second lefthand armature and front contact to ground. Relay |003 now closes a circuit for the start lead ST to seize the first link by the operation o relay |400. The circuit for relay |400 may be traced from battery, upper winding of this relay, contacts of relays |500, |300 and |40!. the start lead ST through contacts of relays 800 and |004 to ground at contacts of relay |003. It should be observed at this time that there are duplicate sets of circuits for the operation of relays. 800 to 803, 901, 900, 902, 00|. |005, I0|2 and |0|3 and other relays. The batteries marked A are in reality a single battery with a fuse not shown between it and the various circuits and similarly the batteries marked B are a single battery with a fuse not shown between it and its various circuits. The purpose of these circuits through duplicate windings and contacts is to prevent breakdown of the circuits of these important relays. For example, if a false ground occurs in one of the battery chains thus blowing the fuse connected at the source-as described, the relays in the chain will nevertheless operate on the other winding from battery through the other fuse. In case a false ground occurs on one of the ground chains the circuits will function normally when calls come in. Under all of the above conditions the circuits are arranged to detect these conditions. Figs. 16 and 17 show such detection or alarm circuits. Therefore, if, for example, one of the chain circuits is opened for the allotter relays, the

relay

809 or 805, as the case may be, will release when one of the relays 800 to 803 operates. This connects ground to the lead CA causing the operation of relay |0|0, this relay in turn closing a circuit over the CAI lead for the operation of relay |608 which locks under the control of the release key and causes the operation of relay |601. This relay closes partially the circuit for the buzzer and the red lamp shown in Fig. 16. When tlis condition is to be ascertained the guard key is operated and the green and red lamps light steadily to indicate this condition. Also in case a false ground appears on the battery chain of relays 901, 900, 903, 90| or |005, |0|2 and |0|3, the operation of relay |0|0 as described will connect the relay |0|1 or |0|8 to the chain contacts for these groups of relays, respectively. Then when the relay |00! is operated at the end of a call, as Will be described hereinafter, -the par- 'cular relay operated in each chain circuit releases and if. no other call is waiting battery will be connected directly to one end of the winding `rf the relay |0|1 or |0|0 through the ground chain circuit and this relay will then operate over a circuit in series with the resistance to ground as shown. Relay I0 I1 or I0 8 operates the relay ISIS and an indication is given as usual. Similarly, if a ground chain is open for one of these groups of relays, or, if at the end of the call the normal ground applied by relay |00| is removed and relay |0|9 or |020 will operate, as normally when relay |0 0 is operated, these relays are connected diierentially to the ground chain circuit. Relay |0|6 will then operate to give the indication as usual. The circuits of the allotter are so arranged that if for any reason the start wire ST is not advanced properly an emergency nath for advancing it under control of the

relays

812, 8|3, 0|0, 801 and 806 is provided. At the time the control circuit grounds the ST lead by Jthe operation of relay |003, ground is also connected to lead H3 which operates relay 8|2. This relay in turn operates relay 8|3. The operation of relay 8|3 operates the relay 8|0 which releases relay 8|2. The release of relay 8|2 releases the relay 8|3 which operates the relay 801 over a circuit from battery through the winding of this relay and its make-before-break contacts, contacts of relay 813 and operated contacts of relay 8H]` to ground on lead H3. Relay 8|3 also opens the circuit for relay 8|0 which releases slowly to permit the above circuit for relay 801 to be closed.

The operation of relay 801 disconnects battery from the primary or right-hand windings of the relays 800, 80|, 802 and 803 and disconnects ground from the right-hand armature of relay 885 and armatures of relay 809. This relay also closes an obvious` locking circuit for itself over lead H3 at its inner left-hand armature and front contact and disconnects ground from the leads 4 and 5 to prevent the control circuit from being seized. This relay also connects ground to contacts of. the even numbered relays, such as 800 and 802. If, for example, relay 802 is operated, the` ground from relay 801 will operate the next relay 003 from ground at relay 001, contacts of relays 806, 803 and 800, through the left-hand Winding of relay 803 to battery. Relay 803 will operate and lock as usual and release relay 802. The release of relay 8|0 removes the short circuit from relay 806 which now operates from battery through la resistance, its winding, contacts of CII,

n'rirelay ,to ground on lead H3. The operation of relay 300 connects battery to the right-hand windings of relays 804, 802 and 808 and prepares a path for grounding leads 8 and l to the control circuit to release it by operation of relay i00i in case it has failed to operate. It also connects ground through contacts of. relay 801 to the righthand armature of relay 805 and the armatures of relay 809. Relay 806 also disconnects the ground from the contacts of the even numbered relays 800, 002. The release of relay 8|0 also reoperates the relays 8|2, 8 I3 and 8|0 which repeat the cycle of operations as previously described. The release of the relay 3 3 short-circuits the relay 801 which now releases. The release of relay 801 disconnects battery from the right-hand windings of relays 80|, 802 and 803 and disconnects ground from the right-hand armature of relay 805 and the armatures of relay 809. It also connects ground to the odd numbered relays 80| and 803 and connects ground to the

leads

4, 5 and 6 to the control-circuit. If any of the numbered relays 800 or 802 were operated this ground from relay 806 will operate the succeeding even numbered relay, for example, if relay 80| were operated, relay 802 will operate from battery through the left-hand winding of this relay, contact of relay 80|, contacts of relays 808 and 808 to ground. This relay then locks and releases the preceding relay 80|. Thus this emergency circuit Will be advanced to the start wire to select the succeeding link regardless of the regular advancement of this wire. Returning now to the operation of relay |400, this relay closes a locking circuit for itself from battery, the lower winding, second lower armature and front contact to ground at the relay |003. This relay also closes a circuit for-the relay |004 from battery to the winding of this relay, lower inner armature and front contact and second lower armature and front contact to the ground at contacts of relay |003. Relay |004 in operating opens the start circuit. Relay 400 further closes a circuit for the select magnet 503 for the rst link from battery, winding of magnet 503, contacts of relay |400 to ground and a circuit for the operation of relay |50| from battery, Winding of this relay, contacts of relays |300 and |400 to-ground. Relay |50|, in turn, closes a circuit for the operation of relay |30| from battery, Winding of this relay, contacts of relay 200, contacts of relay |50| to ground. Relay |30| closes an obvious circuit for the operation of relay |302. Relay |302 closes a circuit for a dial tone to be transmitted over lead B to the calling subscribers line from coil |104 over lead DT. Coil |104 receives dial tone from relay which is given a buzzing action by the circuit from ground contacts of relay |308, |302, 303, relay |100 to battery. The dial tone circuit will not be closeduntil relay |300 is operated as hereinafter' described. This circuit will then extend from coil |104, the DT lead, contacts of relays |300, |5|B, |303, |306 to the B lead. Relay |302 in turn closes a circuit for relay |503 from battery, a resistance, Winding of. this relay, contacts of relays |303, |304 and |302 to ground. Relay |503 closes a circuit for the holding magnet 50| to connect through contacts 504 of switch C the calling line to the first link. The circuit for the holding magnet extends from battery, winding of magnet 50|, the HM lead, contacts of relays ||00 and |005, and the LT lead, contacts of relays |503, and |400 to ground. Magnet 50| closes an obvious circuit for the operation ground, independent of of relay 808 and relay i580 is released. The grounds for the GRP and LT leads are removed and a ground applied on the BT lead to make this line busy. Relay 502 in operating closes a circuit for the permanent signal indication relay EMS from battery through the winding of this relay over the PS lead to ground at relay 502. Relay |500 is now operated over an obvious circuit by the operation oi. relay i503. When the connection is established at contact 508 a circuit is completed for the operation of relay i300 from battery, winding of this relay over the sleeve lead S connected at contacts 508, to the HM lead, to

ground through contacts of relays H00, i005,

i503 and i400, that is, the same circuit used for the holding magnet 50 l. Relay |300 locks over its inner left-hand armature and front contact through contacts of relays 352|, i302 and |40| to the ground through the control circuit. This ground connection also serves to hold thevmagnet 50| operated over the sleeve S independently of the ground through the control circuit. Relay |300 opens the circuit for relay |50|, but this relay is held operated by an obvious circuit through contacts of relay |504 which operate as hereinafter described. A circuit is also completed over the tip and ring conductors through contacts 504, contacts of relays |20| and |200 to battery and ground over windings of relay |504 to operate this relay. Relay |504 holds relay |50| operated as described.

The control circuit is now released momentarily as there is no further need for this circuit until dialing is completed. 'Ihis is accomplished as follows: It should be noted that as soon as relay |300 operates the relay 80| of the allotter circuits for the second link is operated over a circuit from battery, contacts of relay 806, contacts of relay 801, right-hand winding of relay 80|, contacts of relay 800, the GD lead, contacts of relay |300, the GDI lead, right-hand winding of relay 809, left-hand winding of relay 805 to ground. 'I'his holds

relays

809 and 805 operated during the operation of allotter relay 80|. The relay 80| now locks from battery, its left-hand winding, its inner left-hand armature and front contact, the corresponding make-before-break contacts of relays 802 and 803, the right-hand winding of relay 805, and it also`locks through its right-hand winding, from battery contacts of relays 806 and 801, its right-hand winding and its inner righthand armature and front contact, the corresponding make-before-break contacts of relays 802 and 003 to ground through the left-hand winding of relay 809. Relay 80| in operating releases relay 800 by opening its locking circuits through both windings of this relay. Relay 80| advances the start lead ST to the next link. Returning now to relay |300, this relay also closes a circuit for the operation of relay |00|, from battery, its right-hand winding, the RL lead contacts of relays |400, and |300 to ground. This relay in operating closes an obvious circuit for the operation of relay |000. Relay |00| releases relay 900 and relay |000 releases relay 904. Relay 904 releases relay ||00. Relay |000 also opens the circuit for start relay |003 which now releases causing the release in turn of relays |400, |004, |00| and |000. Relays |009 and |0|0 which were operated on the operation of the start relay |003 for test purposes as previously described are also released.

It should be noted thatthe original operating circuit for relay |400 was opened by the operation of relay |300. The relays in the control circuit as shown in Figs. 9, 10 and 11 are now all returned to normal and consequently this control circuit is available `for the establishing of other connections until dialing starts. The relays that are nowoperated in the system due to the calling subscriber removing his receiver from `the switchhook are relays4 |50|, |504, |30|, |302 and |300,` the circuits are now ready for dialing.

i The calling subscriber may now dial `the nurnber of the desired subscribers line which comprises three digits. The rst will select the group of` ten in which the called subscribers line is located, lthe second digit will select `thecalled line and the third digit will select the ringing code to be applied to the called line. The link shown is provided with registering or counting relay groups for recording these three digits. In Fig. 12 the relays |206 to |2|| are the register relays for the first digit. These relays are also used for the registering and storing of the third digit, the first digit being stored on special storing relays |406 to |409 in Fig. 14 The second digit is recorled and stored on the register relays |506 to |5|| in Fig. 15. If now the subscriber dials the first digit by releasing and operating relay to open and close the loop connection over the tip and ring conductors through the right-hand windings of repeating coil |0|, the rst impulse will release relay |504. This releases relay |50| and the release of this relay closes a circuit for the operation of relays ||2 and'|5|3. The circuit for relay |5|2 extends from battery through the winding of this relay, contacts of relay |50|, contacts of relays |4|3 and |302 to ground and the circuit for relay |5|3 extends from battery through the winding of this relay, contacts of relays |5|5 and |5| 4 and from this point on over the same circuit as relay |5|2 was energized to ground at relay |302. Relay |5|2 is slow in releasing and remains operated during the pulsing. When now the pulsing relay |504 is reoperated at the end of the first pulse relay |50| reoperates from battery, winding of this relay, contacts oi relays |5|3 and |5|4 to ground at contacts of relay |504, and relay |50| locks directly to this ground. Then relay V|5|4 is operated over a circuit in series with relay |5|3 from battery through the winding of relay I5I3, contacts of relays |5|5 and |5|3, right-hand winding of relay |5|4, contacts of relays |303, |5|2 and |4|3 to ground at the contacts of `relay |302. When relay |504 was first released it opened the operating circuit for relay |30|, but this relay is slow in releasing so that it remains operated during dialing. Relay |5|4 places a ground on the odd pulsing lead to operate the first register relay |201 in Fig. 12 from battery through the winding of this relay and its make-before-break contacts, contacts of relays |208, |200, |2|0 and |4|3 and |304 to ground at relay |302. The relay |201 is locked through its lower inner armature andfront contact over contacts of relays |208, |209, |2|0, |2|I, |5|6 and |5|2 and from there to ground at relay |302. It should be noted that the right-hand winding of relay |5|4 was shortcircuited by the ground at the outer left-hand armature and back contact of relay |50| so relay |5|4 could not operate until relay |50| has operated. As relay |504 responds to the second impulse by releasing, it causes the release of relay |50| as hereinbefore described and closes a circuit for the operation of relay |5|5. This circuit may be traced from' battery, winding of this relay, left-hand winding of relay |5|4 and operated contacts, contacts' o! relay |50| to ground at relay |302. Relay |5|5`in operating opens the circuit" for relay |5|3 which now releases,` but relay |5|4 remains operated as long as relay |50| is released. When now relay |504 operates at the end ofthe second impulse, Irelay |50| i's again operated overa circuit at this time closed from battery through the winding of relay |50 I, normal contacts of relay |5|3, and operated contacts of reay |5|4 to ground at the contacts of relay |504. Relay |50| locks directly through contacts of relay |504. Relay |50| in operating releases relays |5|4 and |5|5. Relay |5|4 removes the ground from the odd pulse lead and applies it to the even pulse lead and causes the operation of the second register relay |208`in Fig.' 12. The circuit for this relay may be traced vfrom battery, winding of relay |208, contacts of relays |201,

`|5|1, |5I4 and |5|2 to the ground hereinbefore traced at contacts of relay |302. Relay |208 locks over its lower inner armature and front contact and contacts of relays |209, |2|0 and |2|| to the same ground as relay |201 was locked at relay |302 hereinbefore traced. 'Ihe relay |208 opens the locking circuit for relay |201 which now releases. On succeeding impulses incoming to the pulsing relay4 |504 the relays |5|3, |5|4 and |5|5 will operate and function in the same manner. On each odd impulse relay |5| 4 will be operated to ground the odd pulsing lead and on each veven impulse relay |5|4 will be released to ground the even pulsing lead to the counting relays. Thus. the register relays will be operated and released in succession as the impulses are received over the odd and even leads from relay |5|4. The operation of the register relays in response to these pulses is as follows: As already explained the first impulse causes the operation of relay |201 and this relay in operating prepares the circuit for the second relay |208. When relay |5|4 releases at the conclusion of the second impulse this relay is operated as described. Relay |200 prepares the circuit for the odd pulsing lead to relay 209. This ground on the even pulse lead also at this time causes beside the operation of relay |208, the operation of relay |5|6 from battery, left-hand winding of this relay and its left-hand make-before-break contacts, contacts of relay |306 to ground on the even pulsing lead. Relay |5|6 prepares an operating circuit for relays |300 and |5|1 to be operated as will hereinafter be described. On this third impulse,

Relay |5|1 transfers the odd and even pulsing leads to the register relays for the second digit, that is, relays |506 to |5| l, inclusive, which now respond to impulses controlled by relay |5|4 except that in this case the ilrst register relay |501 will operate and lock if only one impulse is received. In this case when relay |5|2 operates on the receipt of the first impulse, relay 5|6 is released. -It should be noted that the original energizing circuit and locking circuit for relay |5|6 through its left-hand winding was opened on the operation of relay |306 while a substitute locking circuit was provided through the righthand winding of this relay and contacts of relay |5|8 through contacts of relay |5|2 to ground at relay |302 when relay |5|2 was released at the end of the rst digit. This locking circuit is now therefore opened and relay |5|6 releases when relay |5|2 operates. Relay k|5|6 releasing prepares circuits for the subsequent operation of relay |5|8 as will hereinafter be described. With relay |5| 6 released and relay |5|2 operated the rst set of register relays will have their locking grounds transferred through contacts of relay |5|2 to ground at relay |302 through the righthand make-before-break contacts of relay 5|6 su that when relay |5|2 is released at the end of the second digit, these register relays will release. However, the reason for releasing the counting relays after'the rst digit has been registered, is.to prepare them for the reception of the third digit. As hereinbefore mentioned, the first digit is stored on the storing relays |406 to I4 I0. The storing of the rst digit as determined by the operation of the register relays, is as follows:

If the first digit dialed is 2, relay |208 is, of

course, operated and this causes the operation of the storing relay |408 from battery, winding of this relay and its make-before-break contacts, contacts of relays |208 and |5| 8 and contacts of relay |306 to ground. However this operation of a storing relay it will be noted does not take placer until the end of the digit when relay |306 is operated as hereinbefore described. The storing relay |408 locks directly through its upper inner armature and front contact to the ground at relay 306. If the first digit is 3, storing relays `that is, relay |401 and |408 will operate. If the digit is 4", relay |409 will operate. If the digit is "5", relays |401 and |409 will operate. If the digit is 6", relay |406 will operate. If the digit is "7", relays |401 and |406 will operate. If the digit is 8, relays |408 and |406 will operate. If the digit is "9, relays 401, |408 and |406 will operate. If the digit is 10 relays |409 and |406 will operate. Whichever combination of storing relays is operated in response to the rst digit, they will prepare, as will hereinafter be described, the control of the switch C to select the group of lines in which a desired subscribers line is located through operations in the control circuit hereinafter described.

Returning now to the transmission of the second digit, it was mentioned that the relays |506- to |6| l, inclusive, operate in the same manner as the relays |206 to |-2||, inclusive. Register relay 5| 0 will operate when the digit is l over a circuit as follows, battery winding of relay |520, contacts of relays |500 and |5|1, lower winding of relay |5|0, contacts of relays |509, |508, |501, |506, |5|1 and |5|4 over the odd lead to ground at relay |302 as hereinbefore traced. Relay |5|0 locks from battery, upper winding and makebefore-break contacts of this relay, contacts of relays |509, |508, |501, |506, |4|3 to ground at relay |302. Similarly other register relays are operated and locked by other digits, relay |509 by digit 2, relay |508 by digit 3, relay |501 by digit 4, relay |508 by digit 5, relays |506 and |5|| by digit 6, relays |5|| and |5|0 by digit 7, relays |5| I and |509 by digit 8, relays |5|| and |508 by digit 9, relays |5|| and |501 by digit 10. At the end of the last pulse of the second digit the register relay or relays which may have operated in response to this digit remain locked under control of relay 4| 3. The locking circuit, for example, for relay |5|0 may be traced from battery through the upper winding of this relay at its upper inner armature and front contact, make-before-break contacts of relays |509, |508, |501 and |506, lower outer armature and back contact of relay |4|3 to ground at relay |302. When now relay |5|2 releases at the end of the second digit, relay |5| 8 operates from battery, winding of this relay, contacts of relays |5|1, |5|6 and |5|2 to ground at relay |302 and locks through its own contacts independent of relay |5| 1. Relay |5| 8 in operating releases relay |5|1 by the opening of its make-before-break contacts. The register relays operated for the first digit are released due to the release of relay |5|2 as the holding ground for these relays was transferred under control of relay |5|2 on the release of relay |5|6. Relay |5|8 also in operating opens at its outer armature and back contact the ground connection from the register relays for operating the storing relays so that no further control can be exercised over these storing relays. After the setting of the register relays for the second digit the circuits function to respond to the third digit, |5| 4 will apply ground to the odd and even pulsing leads which now haveV been transferred byd the release of relay |5|1 back to the rst set of, register relays in Fig. l2. These relays will now respond to the impulses the same as before. When the first impulse is received in addition to operating relay |201, relay |5|6 will now be operated and locks through contacts of relay |5|8 to ground at relay |302. The circuitV