US2185287A

US2185287A - Telephone system

Info

Publication number: US2185287A
Application number: US85459A
Authority: US
Inventors: William M Beaumont
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1936-06-16
Filing date: 1936-06-16
Publication date: 1940-01-02
Anticipated expiration: 1957-01-02

Description

J 2, mm.

W. M. BEAUMONT TELEPHONE SYSTEM Filed June 16, 1936 FIG.

5 Sheets-Sheet l INVENTOR W M BEAUMONT WWW ATTOR/V V Jam. 2, 194G.

w. M. BEAUMONT 2,185,287

TELEPHONE SYSTEM Filed June 16, 1936 5 Sheets-Sheet 2 FIG 3 IOJ o lNl/EN70R W M BEAUMONT BY ATTO/PNE Jan. 2, 194.

W. M. BEAUMONT 2,185,287

TELEPHONE SYSTEM Filed June 16, 1936 SSheets-Sheet 3 FIG 4 INVENTOR WM; BEAUMONT Arron/w M 2, 19 0. w. M. BEAUMONT 2,185.28?

TELEPHONE SYSTEM Filed June 16, 1936 5 Sheets-Sheet 4 IN VEN TOR WM BEAUMONT Jan. 2, H940.

w. M. BEAUMONT 2,185,287

TELEPHONE SYSTEM Filed June 16, 1936 5 Sheets-Sheet- 5 FIG. 6'

RING/N6 ALARM AND INVENmR By n4 M BEAUMONT Patented Jan.2, 1940 2,51%,28?

UNITED STATES PATENT OFi-liilh TELEPHONE SYSTEM William M. Beaumont, Summit, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 16, 1936, Serial No. 85,459 1': Claims. (01. 1'l918) This invention relates to telephone systems ment of this kind in which a single relay is proand particularly to small capacity automatic vided for each link for this purpose and in which telephone systems in which cross-bar switches the relays of two links in the allotter circuit are are employed. always operated. The starter wire is extended 5 An object of the invention is to provide imby the relay of one of said links for the assign- 5 proved and economically arranged systems for ment of said link to be used in the next connecautomatically establishing connections between tion, and when this link is taken for use, this telephone lines and between lines and trunks. relay is released and. the starter wire is extended Heretofcre systems have been provided for to the succeeding idle link and the relay of the establishing connections between two subnext succeeding idle link is then operated. 10 scribers lines in a single switch by means of Another feature is the arrangement for releaslinks at two cross-connecting points only and being a connection between subscribers lines solely tween a subscribers line and a trunk at one in response to the calling subscriber replacing cross-connecting point only. The features of his receiver on the switchhook and an arrangethe present invention have been applied in a ment whereby the release of the called subscriber 16 system of this type as disclosed in the Patent from a connection may take place by the called 2,071,075 of Feb. 16, 1937, to C. D. Koechling. subscriber removing his receiver from the switch- One feature of the present invention provides hook and operating any one of the keys normally for call conference connections in systems of the used for establishing trunk connections as ar- 20 above-mentioned kind. After a connection has ranged in the above mentioned patent. When 20 been established between a calling subscriber the called subscriber replaces his receiver on the and a called subscriber over a link, the called switchhook two relays are released to complete a subscriber may replace his receiver on the switchholding circuit in the link to prevent the link hook and the calling subscriber may then, dial from releasing except by the calling subscriber the number of another called subscribers line replacing his receiver on the switchhook. If the 25 and thereby cause said second called subscribers called subscriber then decides to free his line line to be connected to the same link. Other from, the connection he may, by the operation of subscribers lines may be added in the same manone of the trunk keys cause the reoperation of ner to the conference connection. one of these relays and thereby cause his line The arrangement is such that when the callto be free to establish another call. 30 ing subscriber starts dialing the number of an- Another feature is an arrangement in a system other subscriber, the first called subscribers bell of this kind where a trunk call for a subscriber is rung and when the second called subscriber of a so-called keyless station is first received by answers the call the first called subscribers bell a master subscriber of a sc-called key station will cease to ring as an indication to this first and then transferred to the subscriber of the 35 called subscriber toagain remove his receiver keyless station, whereby the subscriber at the from. the switchhook and thereby cause his line key s ation m y by p r i a y cause i to be connected in the conference connection. line to be freed from the connection established In case the second called subscribers line is busy, 0 the key s Station- ThiS arrangement i 81180 the first called subscribers bell will cease to ring operative when a trunk connection is desired by 40 when the second called subscribers line is seized a keyless station in which case the key station and the calling subscriber will receive a busy sigsubscriber establishes a connection from his stanal. The first called subscriber will answer the tion to a trunk and then transfers the trunk call as usual and be: informed by the calling subconnection to the keyless station.

scriber that the second called subscribers line is This invention has been illustrated in the ac- 45 busy. companying drawings in which:

In the system disclosed in the above-men- Fig, 1 shows diagrammatically how lines, links tioned patent there is provided an allotter cirand trunks are arranged on a cross-bar switch cuit arranged for allotting succeeding links to be in a small capacity automatic telephone system; used for establishing connections. A starter and 50 wire is extended to an idle link when a sub- Figs. 2 to 6 show the various features of the scriber calls and when the link is taken for use invention in detail in a small capacity automatic this starter wire is extended to a succeeding idle telephone system of the general type disclosed link. It is a feature of the present invention to in the patent to C. D. Koechling above menprovide an improved allotter circuit arrangetionedt Fig. 2shows four different types of sub- 55 scribers lines. Figs. 3 and 4 show four vertical units and six horizontal units or levels of a cross-bar switch together with the line equipment associated with the lines to which the vertical units are connected, and Figs. 5 and 6 show one link circuit in detail for recording dial pulses and extending connections to lines and trunks, an allotter circuit for allotting links in rotation and one trunk circuit in detail for extending calls to a central office.

In Fig. i the subscribers have been shownin the vertical units and the connecting links and trunks in the horizontal units. For example, if a connection is to be established between two subscribers lines such as NH and I02, a connection is established from line 50! over the associate vertical unit through the switch to one branch of a link such as 503 and through this link over another branch through the switch and the vertical unit associated with line E02. If a connection is to be established from the subscribers line till to a trunk a connection is made through the switch to the trunk such as N34. The cross-bar switch structures may be of any well known type in which a selecting magnet for a horizontal unit and a holding magnet for a vertical unit may be operated to establish a con nection through contacts at the intersecting points of these units.

In the present system using this type of crossbar switch and embodying the features of the invention, four cliiferent types of subscribers lines have been shown. The subscribers line indicated at A is called a master key station and provided with means for receiving and extending connections to any other station and to extend and receive connections from any trunk, three of which have been arranged in this system. The connections to these trunks may be established by operating corresponding keys i, 2 or 3 of said trunks. The subscribers station E is called a keyless extension station and may establish connections to any other subscribers line in the system, but only receives and extends calls over a trunk through the aid of the master station A, that is, trunk calls intended for or that are to be made from station B must first be received or set up by the station A which then transfers the trunk connection to station B and retires from the connection. Station 0 is also equipped with a key for establishing connections to and from trunks and may establish connections to and from any other subscribers but is provided with means for aiding in establishing connections for extension stations. Station D is a keyless station arranged for receiving and establishing connections to other subscribers in the system, but not trunk connections. To fully understand the features of this invention a detailed description will now be made of the various calls possible over the system disclosed. Calls will be described as follows: A line-to-line call from the master station A to station E, to the key station C and to the keyless station D; a call from line A to a trunk; a call from the keyless station B to a trunk which is accomplished by the aid of station A; conference connection, that is, a call, for example, from station A to station C and then to station D to bring these two stations into a conference connection with station A; calls incoming from a trunk; transferring calls from a trunk from one station to another and calls from a trunk to keyless stations and for emergency calls from master station A.

If the call is made from station A the sub scriber at this station will remove his handset 200 from the switchhook and operate the key L. This closes a circuit for the operation of relay 400 from battery through the winding of this relay, contacts of the holding magnet 40!, of the vertical unit over which a connection may be established from station A to one bank of the link shown in Figs. 5 and 6, over the R lead, contacts of the emergency key 202, the left-hand and middle winding of the repeating coil 203, Oilnormal contacts of dial 204, switchhook contacts, contacts of emergency key 202 over the T lead, make-before-break contacts of relay 400, contacts of relay 602 to ground. The operation of this relay closes a circuit for the start relay 500 and the relay 50! which is individual to this particular line over a circuit from battery, winding of relay 500, contacts of relay 690, which is operated and is the first relay in the allotter circuit that allots the first link to be used for the next call, contacts of the second allotter relay '60! which is also operated back over the start lead ST, contacts of relay 400 over the L lead to contacts of key L, contacts of

keys

3, 3 and I, over the G lead, through the switchhook contacts and contacts of key 202, contacts of relay Q00, winding of relay 55! to ground at contacts of relay 503. The operation of the relay 50! closes circuits for the operation of relay 504 from battery, winding of this relay, contacts of relays 565 and 5125 and other intermediate relays, not shown, but of which one is provided for each link as will hereinafter be apparent, left-hand armature and front contact of relay 50! to ground at contacts of relay 5133. Relay 501 is now operated from battery through the winding of this relay, contacts of relays 558, 509, and 50! to ground. This relay in turn operates relay 509 which is slow in operating. Relay 50 3 closes a holding circuit for itself to ground at contacts of relay 50! and closes a circuit for relay 503 from battery, winding of this relay, contacts of relay 5:18, contacts of relay 554 to the ground at relay 50L When relay 503 operates the operating circuits from all the other relays individual to the different lines such as 5H1 serving the same purpose as relay 50!, are opened to prevent any other call from proceeding at this time. The operation of relay 5523 operates the relay 508 which is slow in operating over a circuit from battery through the winding of this relay, contacts of relay 503 to ground at contacts of relay 50! and this relay in turn closes a locking circuit for relay 563 while relay 507 releases slowly. Relay 588 releases relay 599 and connects ground to the SMS lead for the operation of the select magnet of the allotted link over the OSM lead. In this case this select magnet is marked Si and the circuit may be traced from battery through the winding of this magnet SI, the OSM lead, contacts of relays 5H, 586, M2, 508, to ground at relay 5M. This insures holding operated the relays 558 and 503 until all other relays are released which will prevent a double connection. That is, in case the circuit from the operating ground of the operated relay 50! to the relay 504 is opened, relay 5% will fail to operate which will also fail to operate relays 553 and 500. As previously mentioned relay Ell! operates relay 507 which operates relay 509. The operation of relay 508' releases relay 507. With relay 501 released and with relay 509 operated a ground is connect-ed to the SNS lead to operate the select magnet. This insures service in case relay 504 does not operate due to its operating circuit being opened at one of the contacts of the relay 50l or relay 505 or 506 of that group.

The operation of the select magnet SI moves the usual fingers oi the select bar in this level.

It also operates relay 5M over a circuit from battery through the winding of this relay, contacts of select magnet S1 to ground. Relay 5M closes a locking circuit for relays 5&8, 503 and 5M. Relay 5M also connects a ground through the A lead to close a circuit for the cut-off relay 462 from battery through the winding of this relay, the A lead, contacts of relay Elli, contacts of relay 514 to ground. The cut-ofi relay M92 closes a connection to ground for relay 50! to shunt this relay and cause it to release and closes an obvious circuit for the holding magnet Ml! of the vertical unit in the switch to connect the calling line to the originating branch of the link shown in Figs. 5 and 6 at the cross-connecting point 406. When this connection is established relay 492 locks from battery through the winding of this relay over contacts at the connection made at the point l lli, L lead, the L key and the

trunk keys

3, 2 and l at the subscribers set, the G lead, through the switchhook contacts, contacts of key 202 back to ground at the lower armature and front contact of relay 402. The operation of the holding magnet 40! releases relay Mill and connects ground to the CO lead which extends to contacts of the counting relays shown in Fig. 6 as will hereinafter be described for busying the calling line to incoming local calls. The connections for the T and R leads extending over the cross-connecting point 406 to the allotted link now causes the operation of relay 5|! through the calling subscribers loop, contacts at the cross-connecting point 486, the tip conductor, upper winding of relay 5H, contacts of relay 500 to ground over the DT lead to the tone ringing alarm and common timing circuit indicated by the box Eli? and the ring conductor to battery through the lower winding of relay 5H. Relay 5!! closes a circuit for the operation of relay 5!! from battery through the winding of this relay and its makebefore-break contacts, contacts of relay 5!], over lead Sl to contacts at the cross-connecting point 486 to ground at contacts of relay Q02. Relay 5!! in operating opens the circuit for the select magnet Si and this relay in turn opens the circuit for relay 5M which causes the release of relays 5B5, 508 and 503. Relay 5 locks from battery through the winding of this relay and its upper inner armature and front contact directly to the Si lead. It will be noted that on the operation of relay 500 a connection was made through its lower outer armature and front contact to ground over the lead DTS to the tone circuit 603 to start the dial tone. Dial tone is now transmitted over the DT lead, contacts of relay 580, the upper winding of relay 5, over the tip conductor to the calling subscribers circuit back through the lower winding of relay Ell and battery.

The operation of relay 5!! also transfers the start lead for the allotting of the next idle link for the next call. It should be noted that the circuit for relay 60% is opened at the upper outer armature and back contact of relay 5! I. This releases relay Gilt and a circuit is now closed for the operation of the next succeeding allotter relay Sill from battery through the winding of this relay, contacts of the relay in the third link correspond.- ing to relay 5M to ground at the make-beforebreak contacts of relay 660. The operation of the relay 801 connects the second link by extending the start wire ST over the upper outer armature and front contact of relay 60!, upper armature and back contact of relay 600, lower inner armature and front contact of relay 60! to the start relay in the second link corresponding to start relay tilt of the first link. Should the second link be taken for use, relay Bill will release and relay Elli! r'eoperates. The circuit for relay Silt in this case would extend from battery, winding of relay iillmcontacts of relays 5i! andfiil! to ground and the start wire will then be extended over the upper outer armature and back contact of relay til i, upperouter armature and front contact of relay Gill for the allotting of the third link. Thus it will be seen that only a single relay will be required for each link in this allotter circuit with relays of two succeeding links maintained normally operated. If all three links are in use the start lead will not be extended until one of the links becomes idle when the start relay of this idle link will be operated by the circuit closed by the next preceding start relay being operated. to extend the start wire tothis link.

The subscriber upon receiving the dial tone now operates the dial which will release and operate the relay 5 IT in unison with the make and break of the dial contacts. The relay 520 operates when the relay fill releases on the first impulse of each digit and remains operated until the end of the last pulse of each. digit The circuit for relay 52d may be traced from battery through the winding of this relay,contacts of relays 52L Eli and 5!], over the S! lead, contacts at the cross-connecting point 406, contacts of relay 402 to ground. On the first pulse and subsequent odd impulses the relay 522 operates when the relay 5!! releases over a circuit from battery through the Winding of this relay, contacts of relays 52!, 523, 5H and 5|! to ground on the SI lead. For the second pulse and subsequent even impulses the relay 52! will operate and the relay 522 will release. The relay 522 when operated connects ground to the odd lead to operate the odd number register relays, and when relay 522 is released it connects ground to the even lead to operate the even register relays. These registers can only operate While the relay 520 is operated. The numbering system used in the present invention which provides for twenty subscribers lines as indicated in Fig. 1, may be numberedfrom 20 to 39. Relays 52!, 522 and 523 operate and release in the following manner. When relay 5!! re-- leases on the first pulse the relay 522 operates from battery through the winding of this relay, contacts of relays 52 l, 5H and 523 to the Si lead. When relay Ell reoperates relay 523 operates over a circuit from battery, winding of relay .523, contacts of relays 52! and 522, left-hand winding of relay 523, contacts of relay 520, make-beforebreak contacts of relay 52s to ground at contacts of relay 556. It should be noted that on the operation of relay 522 a circuit was also closed for relay 525 from battery through the winding of this relay and its make-before-break contacts, contacts of relax e635, 522 and 52!! to ground at relay 5! 1. When relay Ell releases on the second impulse, relay 552i will operate over a circuit from battery through the winding of this relay, righthand winding of relay E523, contacts of this relay and contacts of relays 5H and 5!? to ground on the Si lead. The operation of relay 5M releases the relay 522 and transfers the operating circuit of relay 529 to a holding circuit from battery through the winding of relay 528, contacts of relays 52i, 520, 52A to ground at contacts of relay 5i i. The purpose of this is to remove any shunt 522 will operate and 523 release, with relay operated on the odd impulses and released on the even impulses. It should be noted at this point that in the case of a momentary opening of the line before a digit has been dialed the relay 5!? will release and relays 526 and 522 operate. When relay 522 operates, and causes'relay 525 to operate, relay 525 will be held operated under control of relay 529, then when relay '5l'l rec-perates relay 523 will release, releasing these

relays

522 and 525 to again prepare the circuit for the reception of the first digit.

, .The efiect on the register relays of these pulses of the first digit will now be described. As stated when a first impulse is received relays 52.2 and 525 operate and when relay 522 releaseson the second impulse of the first digit relay {Hi5 operates over a circuit from battery, winding of this relay and its make-before-break contacts, contacts of

relays

525, 522, 526 to ground at relay 5H. This relay in operating looks over its inner left-hand armature and front contact to the common ground at contacts of relay 553 over make-before-break contacts of relay 52 i. Relay 5% releases the start relay 55!! by opening the connection at its outer right-hand armature and back contact and closes the odd leadfrom contacts of relay 52! for the subsequent operation of relay 6H3. Therefore, when the first impulse is received this relay will operate from battery through the winding of this relay M and its make-before-brealr contacts, contacts of relays SH, 625, 885, 522, 52d to ground at relay l. Relay Bill locks over a circuit from battery through its winding and inner left-hand armature and front contact to ground on the common lead. Relay 6E0 closes the even lead from relay 522 to relay 65! so that when the fourth impulse is received relay 6H will operate from battery through its winding; contacts of

relays

816, 525, 522, 526 to ground on relay 5i i. The operation of relay 6H prevents this fourth impulse and subsequent impulses if dialed on the first digit from establishing any connection to any station as in this system there are only two groups of ten subscribers each to choose from so that the third impulse in this case when received will choose the second group of ten subscribers lines W to 39. In case only two impulses have been received the first group of subscribers lines 26 to 29 would have been chosen. Assuming that three impulses are received on the first digit the relay 525i will release at the end of this digit and relay 525 which is locked through the lower armature and front contact ofrelay 522 will also release at this time. Relays i305 and 5!!) are therefore the tens digit or first digit register relays. The odd and even relays are now transferred to the unit or second digit register relays 6E2 to till. On the first impulse of the second digit relays 522 and 5520 are operated and relay 528 in this case causes the operation of relay 52'! over a circuit from battery, winding of this relay and its niake-before-break contacts, contacts of relays 555, 525, 52!; to ground at 5! 5. Relay 522 in operating connects ground to the odd lead and in releasing to the even lead to operate relays (N2, M4 and MS over the odd lead and relays 653, M5 and Bil over the even lead. In operating these registering relays of relay hi5, and relays E515 will release on the operation of relay, Gila, but when relay 3|! operates relay tiiS will remain operated and when more than six impulses are dialed relays 6l2,

EH3, 6M and M5 will operate and release in the order named. When relay M2 operates on the seventh impulse relay 656 will release. example of the operation of this relay on a first impulse relay 6l2 will operate over a circuit from battery through the winding of this relay and its make-before-break contact, contacts of relays hi3, EH6, EH5 over the odd lead, contacts of

relays

525, 6% and 520, to ground at relay 5i i. On the second digit relay 522 releases and relay M3 is operated over a circuit from battery, winding of this relay, contacts of relay 525 over the even lead through contacts of relays v 522 and 529 to ground at relay 5! l. When relay hi3 operates, the holding circuit established through the make-before-break contacts of this relay for holding of relay 652, is opened so that this relay will now release. for relay N3 is established over the operated armature and front contact, make-before-break contacts of relay 5H3. At the end of the last impulse of the second digit relay 5% will release and as relay 52? is operated relay 6! i will operate if not already operated by a fourth impulse. The circuit extends from battery through the winding of this relay, its make-before-break contacts, contacts of relays 52'! and 529 to ground at relay 5! l. armature and front contact to the common ground lead. Relay 6 closes a circuit for the operation of relay 525 from battery, winding of this relay, contacts of relay 6i i to the common ground. This'relay also connects the busy test relay 5% to the CO lead of the line selected as will hereinafter be described, and opens the operating path for relay Bill to prevent it operating in case a third digit is dialed when this relay is not operated and connects the common leads together which connect to the CO leads through the contacts of the register relays. These leads are shown at (M8 for lines shown in the cross-bar switch and it is to be understood that others are connected to contacts of the register relay. Connections to these leads are open until dialing is completed to prevent two CO leads from being tied together, as the ground on one CO lead from a line, line switch, or call allotter circuit, would cause interference to another line by connecting this ground to another CO lead while the register relays are operating and releasing. If it is assumed that the line 28 was dialed, that is the first digit was 2 and the second 8, the relays aw, Gil and M3 will be operated. The circuit will now therefore be closed at the end of the second digit due to the operation of relay 52? for relay 533 as follows: battery, winding of this relay and its make-before-break contacts, contacts of relays 52?, Eli, Gill, 6!], M3, over lead 28 to the CO lead of the called line which may be line C. If this line is busy there will be a ground on the corresponding CO lead applied by the holding magnet 352 thus causing the operation of busy-test relay 530. This relay will lock over its upper inner armature and front contact to the common ground lead. As relay 5355i operates the original energizing circuit will, of course, be opened at the make-before-break contacts and consequently no interfering ground or battery Asanz,

The holding circuit Relay 6H locks over its inner left-hand toground at relay W3. lay 563 from battery, winding of relay B3, conr to ground at relayt'atli. the terminating or called branch of the link is busy-tone circuit is also closed and a busy tone transmitted to the calling. subscriber. A connection is made to ground for the BTS lead for starting the busy tone equipment tilt and the busy tone is then transmitted from this source over the BT lead through contacts of relay 5% over the tip lead of the calling line through condenser 53!. I

If the line is not busy the relay 525 in operating after the completion of the second digit closes Li and L2 leads for the operation of relay 585 individual to this link, from battery over the winding of this relay, contacts of relays 53G, $255, 52?, 503 to ground. This relay in operating closes a circuit for the operation of relay 532 from battery,

winding of this relay, contacts of relays 5&5, 552i, 520 and ground at relay 5i i. Relay 5% in operating also closes a circuit for relay 594 from bat tery, winding of this relay, contactsoi relay 565 Relay 5% operates retacts oi relays 59B and 56 5 to ground at relay 5%. RelayfillS closes a circuit for relay 5% from battery, winding of this relay, contacts of relay 583, The select magnet Sfi of now operated to connect this branch to the called line. The circuit may be traced from battery through the winding of this magnet S4, contacts of relays 535, 532, 588 to ground at relay After magnet S l operates it closes an obvious circuit for the operation of relay 5M and this causes the rel-ease of relay 52'l, as the battery for the circuit of relay bill is shunted through contacts of relays 5&5 and 5M to ground. Relay 532 is released by relay 527. The cut-oil relay 30 i of the called line C will now be operated over a circuit from batterythrough the winding of this relay over the corresponding CO lead to a circuit hereinbefore traced over contacts of relays operated in the register, namely, 6E3, til and till! to ground at the upper armature and back contact of relay 5521. holding magnet 302 which therefore establishes a connection at the cross-connecting point 306 in the switch for the terminating branch or" the link used. When this connection is made relay 533 is operated to connect ringing current to the called line. This circuit may be traced from battery, winding of relay 533, contacts oi relay tilt over the S2 lead through the cross-connecting point at 308 to ground at contacts of relay 3%. As magnet 362 operates relay 3% is removed from the connection over the CO lead to ground but after the connection is established through the crossconnecting point at 3% this relay will be held through contacts of relays 5! i, Mi, over the Si lead through the cross-connecting point at art to ground at relay 402. The ringing current is now transmitted from the source at 6&3 over the ring conductor, the upper inner armature and front contact of relay 533, condenser 52% to the ring conductor of the called line through the crossconnecting point 3%, ring conductor to the calling subscribers ringer and back over the tip conductor, the cross-connecting point at 3536, the lower outer armature and front contact of re lay 533, back to the source 5%, while a direct current path extends from the conductor at 603, through the subscribers set when he answers over the ring conductor tip through the upper armature Relay Silt operates the and back contact and upper winding of the ringing tip relay 539, contacts of relay 530, the upper outer armature and back contact of relay 533 to the ring conductor at 603. The subscriber on the line C will now in answering this call remove his receiver from the switchhook thus causing ringing tip relay 539 to operate on the next silent interval. This subscriber will also operate the key L and this causes the operation of relay 524 from battery, winding of this relay through the cross-connecting point at Sill over the L lead to the key L, the

trunk keys

3, 2 and l, switchhook contacts over the G lead to ground at relay 384. Relay 5% opens the common ground lead which holds therelays 525, 595, 6! l and the register relays operated thus causing the release of these relays. The release of these relays removes the ground from the CO lead to the called line and the release of relay 6% causes the release of relay 533, thus stopping the transmission of ringing current to the called line. A circuit is now closed for the operation of relay 536, over the tip and ring conductors from battery and ground through the two windings of relay i538 and contacts of relay 533 over the called subscribers loop. Relay 536 in operating releases relay 539 which was looked through its lower winding and lower armatureand front contact through contacts of relay 536 to the common ground. Relay 53% opens a connection to ground for the S lead and a substitute ground is connected to this lead at the upper armature and front contact of relay till. The connection between the calling and called subscribers is now established with relays til i," Ell and 536 operated. Conversation between the calling and called subscribers may now take place with talkingbattery for the calling subscriber supplied through the windings of relay EI'I and for the called subscriber through the windings of relay 536.

In case this call had been for a keyless station, such as D, the operation of relay 3% and the holding magnet 36'? take place in the same manner as the operation of the corresponding relaysand magnet of station B. In this case when the called subscriber answers relay 539 is operated. The connection for the leads TR and L are tied together as shown at the point EH2 and in this case therefore the relay 524 will be operated from battery, winding of this relay over the L lead back over the TR- lead through contacts of the operated relay 539 to ground at contacts of relay 5| l. Relay 52! opens the common ground lead which holds the relays 525, 565 and ti! and the register relays which are now released. The release of'relay tilt releases relay 533 and stops the ringing and when relay 5% operates it is connected to the line by the release of these relays and will release relay 539 and open the circuit for ground to this lead. Relay 536 also connects ground to this TR. lead which holds the relay 52d operated.

In releasing the connections in case the calling party disconnects first, the called party will be held to the link until the receiver is replaced on the switchhook. This prevents the called party being disconnected from a link and then connected to the originating end of another link and receive dial tone. When the called party releases relays 524 and 536 are released thus "permitting the release of the called party. If the calling party disconnects first relays Eli and 5 will be released but relay 3% and holding magnet 3512 will not be released as relay 3% is held operated over the S lead by relay 524 as the opening of the circuit for relay 402 and consequent release ofthe magnet dill, relay releasing by the opening of the L key by the calling party.

In the case of a call from a subscribers line to a trunk, for example, from the key station C to thefifirst trunk shown in Fig. 6 the subscriber at the key station C will remove his receiver from the switch-hook and operate a trunk key I. Relay 3H5 is then operated from battery, winding of this relay, contacts of relay 362 through the subscribers loop, make-before-break contacts of relay till to ground at contacts of relay 306. The holding ground for this'relay is now transferred to a ground in the tone ringing alarm circuit specified at 603. The purpose of this transfer is to provide a means to transmit a busy tone to the station in case the trunk selected is busy. If the trunk is busy a relay in the tone circuit at Gilt will operate, which will transfer the holding ground from the relay 316 in this case to ground through the winding of a repeating coil and with the operation of other relays a tone will be transmitted to the station through the windings of this coil. The operation of relay 3E6 closes the leads 5, ii'and 3 from the trunk key at the station C to the CS leads of all the trunks, the L lead to the ST lead of the link and link allotter circuit at the station lead G to the G lead in the link circuit. These leads are, of course, kept open until the relay (H6 is operated for the purpose of preventing service interference in case one of these leads has become grounded. The G lead is the common lead to the station and when the switch-hook is released by the removal of the receiver this G lead is closed through switchhook contacts to the various keys in the station. As key l is provided for trunk l and is operated, a circuit is now completed over the G lead for the corresponding relay such as the relay or 590 in the link. The particular relay for this station has not been shown but it operates in series with relay EiZii in the first trunk, also a circuit from battery, Winding of relay 628, contacts of relay 82!, lead CSLO, contacts of relay 3m over the G lead for the first trunk, contacts of the first trunk key over the ,G leadand contacts of the switchhook contacts, of relay 3l6 to the relay corresponding to relay 505 or relay 569, not shown, to ground at contacts of relay 5%. Relay iiZtl closes acircuit for relay 5i? from battery, winding of this relay, contacts of relay 629' to ground. This opens the connection for the SMS lead that ordinarily provides ground for the operation of the select magnet of the corresponding allotted link ordinarily seized when the lineto-line call is made. In this case the link will not be required. In this case the relays EM, 509, till, 535 and 588 will operate as hereinbefore de-' scribed and provide aground connection for the operation of the select magnet 495 for the first trunk over a circuit as follows: battery, winding of magnet 405, contacts of relay 62E, SMtSl lead,

I contacts of relay 5198 and the relay corresponding to relay 5B! or 5H) to ground. Magnet M closes the usualcircuit for relay 5M and this relay in turn closes a connection at its lower inner armature and front contact to ground for the A lead through a relay corresponding to relay Sill or 5H) over the A lead through the winding of relay 304 to battery causing the operation of this cut-on relay. Relay 3% closes a-circuit for holding mag net- 302 to connect the line C at the cross-connecting point 3E8 to the conductors of the first ,1 ,28 stated while the calling party will be released by trunk. Relay 304 in operating closes a connection at its upper armature and front contact to ground for the G lead and this ground is extended over ,a subscribers loop through key I through the contacts at the cross-connecting point 3H3 through the winding of relay 304 to battery. This placing of a ground on the G lead releases the relay corresponding to relay 50! or 5H1. The operation of the holding magnet 30? opens the circuit for relay 3! B which now releases to open the CS leads between the station C and the trunks. Consequently, relay S23 is released and this causes the releaseof relay 5E2 and the select magnet d815,. Magnet 365 in turn releases relay 5E4 which causes the release or" the operated relays 5634, Ellis and 503. The release of these relaysprepares the circuit for the establishing of another call. A connection from the station C to the central ofice over the first trunk is now established from the tip and ring conductors over the cross-connecting point BIB, through the windings of relay 622, contacts of the emergency key 2% at the key station A out over a trunk to the distant orfice. the operation of relay 304 a connection is established to ground on its lower inner armature and,

front contact through the connections at the cross-connecting point 3l8 over the S! lead, through the winding of relay 62l to battery for the operation of this relay. This relay in operating opens the circuit for relay 629 over the CSLO lead, to prevent stations arranged for nonlock-out service from being connected to the trunk when the line is busy and to close a circuit for the signal lamp 623 which may be provided in this oiiice as a busy signal. It also opens the circuit for a ringing bridge relay 624 and connects the CSLO lead to a tone circuit lead TS at 603 to provide a busy tone to a calling subscriber having a lock-out service. When this connection isreleased by the subscriber at station C replacing his receiver on the switchhook and releasing the trunk key S the relay 32A is released causing the release of the holding magnet3t2 and the ground removed from the SI lead which releases relay 62! in the trunk. Relay 622 is also released.

Description will now be made of a connection to a trunk from the keyless station B which must be set up by the subscriber at the master station A. The subscriber at the keyless station B must make a manual request to the subscriber or operator at station A to establish this connection. The subscriber at station A will select a trunk and connect his station to the trunk as hereinbefore described. Then the subscriber at A will operate the control key and the operator of the keyless station B will remove his receiver from the switchhook. This will operate the relay MD from battery, winding of this relay, contacts of the holding magnet 4H through the subscribers loop at station E, make-before-break contacts of relay MB to ground at contacts of relay H2. In

this case there will be a connection for the associated relays 5M to 510 over a G lead through the control key at station A due to the operation of relay 4H This'connection may be traced from ground at relay 503 winding of the corresponding relay over a G lead, contacts of relay Mil, lead [2 contacts of the control key, lead L over the connection at the cross-connecting point M4, which was established when the subscriber's line at A was connected to the first trunk, lead I, over contacts of the control key, lead 5 contacts of relay 4H), lead CSNL winding It should be noted that on.

of relay 620 to,

412 from battery, Winding of this relay over the A lead contacts of the relay corresponding to 50] or Elli to ground at relay 5M as it will be remembered that when this corresponding relay operates it causes the operation of the relays 594, 503, 5%, EM, 569 in the manner described and then causes the operation of the select magnet 405 asecond time and the operation of relay 5E4 to establish this connection for the operation of relay M2 over the A lead. Relay M2 in operating operates the holding magnet 4H and thereby connects at the cross-connecting point 418 the calling subscribers line at station 18 to the first trunk. The subscriber'at station A hearing the subscriber of station B in on the trunk connection will release the control key. As the relay M2 is operated the usual connection is established for the Si lead to hold relay 62! operated as it has already been operated by relay 402 so that the subscriber at B will now have complete control over the connection over the trunk. The subscriber at station A may therefore disconnect his line from the trunk by replacing his receiver on the switchhook and releasing the trunk and central keys. This releases relay 402 and hold magnet Mill in the usual manner to restore the switch to normal.

The subscriber at station A or C may after he has secured a trunk to the central office hold this trunk so that it may be seized by any of the restricted service stations or for that matter by any other station. This is done by operating the holding key H by the subscriber at station A. This closes a circuit for the operation of relay 6% in the trunk connected to this line. The circuit may be traced from battery winding of this relay over a connection at the cross-connecting point M4, the H lead, the H key, the G lead over the switchhook contacts, contacts of key 202, back over the G lead to ground at the lower armature and front contact of relay 402. Relay 626 looks under control of relay 62!. Relay 626 opens at its make-before-break contact the trunk connection towards the station and connects resistance tZl across tip and ring conductors towards the central ofice to hold the connection at the central ofiice and to hold relay 622 operated from the central ofiice connection. Relay 626 also closes an obvious circuit for relay 628 and opens the S lead towards the line. This, however, periorms no function at this time. Relay 828 closes another holding path for relay 622 at its outer right-hand armature and front contact to hold this relay operated when relay E releases as will hereinafter be described. Relay 828 also closes a circuit for keeping the lamp 623 lighted when relay 62! releases. This relay also connects the CS lead to the relay 620 after the relay til is released to permit the trunk to be picked up. Relay 528 closes a locking circuit for itself through contacts of relays MI and 622 when 625 is released. When the holding key H at the station A was o erated the operators trunk key for trunk releases automatically and this removes the ground from the SI lead which releases the relay 52!. Relay 6M releases relay 626 and connects relay Mil to the CS lead through contacts of relay 628 and closes a holding circuit for this relay 0328. Relay 62E! is slow in releasing to insure the holding of the relay 626 until the tip and ring leads are open at the cross-connecting point M5 which is opened when the holding key operates and the subscriber at A replaces his receiver on the switchhook due to the release of relay 482 and the holding magnet This held trunk may now be sized by a key station, such as A or C, or by a keyless restricted service station, such as D. In case the station C takes the trunk, the connection to this trunk is established as hereinbefore described by the operation of the relay 621i. Relay E20 again closes a circuit for operating the select magnet 405 associated with the first trunk which is held and the corresponding holding magnet 302 is operated as described to connect station C to the first trunk. The tip, ring and Si leads will again be closed to the trunk and the ground on lead SI causes the operation of relay 62 I. This relay releases relay 628' which removes the bridge through the resistance 621 across the trunk, otherwise relay 62! performs the same function as described in connection with the seizure of the trunk as hereinbefore described; The release of relay 528 transfers the CS leads from the relay 620, windings to the CS lead in the tone ringing alarm circuit at 603 to make the trunk busy. The release of the trunk is the same as hereinbefore described in connection with a regular trunk call. If the restricted service line at station D calls to connect with this held trunk it will be noted that, on the operation of relay 320 when the subscribers station D removes his receiver from the switchhook, a circuit is completed from ground through the contacts of this relay over the CSRS leads, contacts of relays 630, 628, 52L winding of relay 62B to battery to operate this relay 620 in the usual manner and seize the trunk in the same manner as a key station.

If a trunk is held and it is released at the cen-- tral ofice relays522 and 628 will merely release and restore the trunk to normal.

A, call incoming over this trunk to a subscriber at this exchange operates relay 624 by ringing current incoming over tip and ring conductors. This relay closes a circuit for the operation of relay 633i which closed a locking 'circuit for itself I under control of relay 62! to ground in the tone ringing and alarm circuit over the LK lead. If the call is abandoned'relay 624 will cease to 0p erate and after a time interval the relay in the tone ringing alarm circuit 6513 which holds the ground on the LK lead will release to release relay $30 and restore the circuit to normal. On the other hand, the operation of relay 630 closes a circuit for the trunk lamp 523 to the tone and ringing alarm circuit at 603 which causes this lamp to flash and connects theCSRS lead to the circuit for relay 520 so that a restricted service subscriber at station D cantake up the call. When the trunk is seized by, one of the subscribers and relay 62! operates, relay 63B is released disconnecting the lamp 523 from the alarm circuit 6% and restores the tone ringing and alarm circuit connections to normal.

In case it is desired to establish a conference connection between several subscribers lines in the system, the procedure may be as follows. For example, if station A calls station C in the regular manner and then desire a conference connection with station D,.the subscriber at station C replaces his receiver which causes the release of

relays

524 and 536. The. release of relay 536 closes a circuit for holding the line of station C connected at the cross-connecting point 3% by maintaining relay 3M operated over a circuit from battery through the winding of this relay,

lead S, contacts of relays 536 and 5, lead SI, contacts at the cross-connecting point lllfi, contacts of relay 582 to ground. The subscriber at station A then dials the number of the desired subscriber which is the line D in this case. When the first digit is dialed the relay 685 is operated which then operates relay 533 which causes the ringer at thefirst called station'to operate, as hereinbefore described, that is, the station C is called by the operation of this relay. When the second called station line is connected to the link in the same manner as the first line was, the ringers of the two called stations will ring simultaneously and when the second called subscriber stationjD answers the ringer at the first called subscribers station (3 willcease to ring as well as the ringer at'the second called subscribers station D and thiswill indicate to the first called subscriber that-the second called subscriber has answered. The first called subscriber now removes his receiver from the switchhook. In case the second line is busy the relay 536 will operate-when the line is tested which will cause the bell at the first called station to cease ringing. and the calling subscriber to receive a busy signal. The first called subscriber will then answer and operate relay 52d releasing relay 530 and all the register relays. I

In case either an incoming or outgoing trunk call is to be transferred from one subscriber to another the station from which the call is to be transferred operates the holding key to hold the trunk as hereinbefore described and the station to which the call is to be transferred may be called locally by depressing the L key and dialing asusual. The station called must then be informed to which trunk the call is to be made. To connect to the trunk hemust then operate the proper trunk key as usual. 7

At station A the key 202 is provided for socalled emergency service to a central oilice. With the key normal, incoming and outgoing central office calls are handled in the normal manner. When the emergency key 292 is operated, however, the trunk shown is'split and the station is connected directly to the central ofilce end of the trunk thereby enabling the station to iunction as a common battery subscribers line for receiving a central office call. It is unnecessary to operate any'of the trunk keys at this station in order to receive a central oifice call when this key is operated. It is seen that the incoming tip and ring conductors will in this case be connected directly to the line by the operation of this key and the connection through the trunk equipment will be opened. As stated akeyless restricted service station 1) may make outgoing calls over a trunk if a, trunk is held. On the other hand it will be noted that ordinarily this station D cannot make any outside trunk calls. If one is attempted and relay 325i operates, the ground on the CSRS lead will be connected through contacts of-relays 633 andfiiiS to the lead TS going to the tone alarm circuit 863 which causes a busy signal to be transmitted over the BET lead-through contacts of relay 329 a certain interval after the connection through the TS lead is made.

What is claimed is: v

1. In a telephone system, a cross-bar switch, subscribers lines terminating in said switch, links terminating in said switch, means responsive to the dialing of two series of impulses over a calling subscribers line for connecting said calling line to a corresponding first called line line over the same link used for connecting the firstc-alled subscribers line to the calling subscribers line and for signaling the second called subscriber, and means for discontinuing the signaling of the first called subscriber when said second called subscriber answers the call.

2. In a telephone system, a cross-bar switch, subscribers lines terminating in said switch, links terminating in said switch, means for establishing a connection from a calling line to a called line through a link and signaling the called subscriber, means responsive to the called subscriber answering the signal by removing his receiver from the switchhook for causing said signaling to cease, means for thereafter establishing a connection from the calling line to another called line through the same link, signaling the second called subscriber and for again signaling the first called subscriber if he has in the meantime replaced his receiver on the switchhook, and means responsive to the second calledsubscriber answering the signaling by removing his receiver from the switchhook for causing the signaling of both the first and the second called subscriber to cease.

3. In a telephone system, a cross-bar switch, subscribers lines terminating in said switch, links terminating in said switch, means for establishing a connection from a calling line to it called line through a link and signaling the called subscriber, means responsive to the called subscriber answering the signaling by removing his receiver from the switchhock for causing said signaling 3 to cease, means for thereafter establishing a connection from the calling line to another called line through the same link, means operative during the establishing of said last-mentioned connection for signaling said first called subscriber if he has in the meantime replaced his receiver on the switchhook, means operative when the last-mentioned connection has been completed for signaling said second called subscriber, means responsive to the second called subscriberanswering the signaling by removing his receiver fromthe switchhook for causing the signaling of both the first and the second called subscribers to cease.

4. In a telephone system, a cross-bar switch, subscribers lines terminating in said switch, links terminating in said switch, means for establishing a connection between a calling line and a called line through a link and signaling the called subscriber, means responsive to the called subscriber answering the signal by removing his receiver from the switchhook' for causing said signaling to cease, means for thereafter establishing a connection from the calling line to another called line through the same link, means opera-- tive' while the second call connectionis being made for signaling said first called subscriber if he has in the meantime replaced his receiver on the switchhook, means operative if the second called subscriber is found busy for causing said last-mentioned signaling oi the first called subscriber to cease and a busy tone to be transmitted to the calling subscriber.

5. In a telephone system, across-bar switch, lines terminating in said switch, linksv terminating in said switch, means forestablishing a connection from any calling line to any other line through an idle link, an allotter for said links, said allotter includinga single relay for each link with a relay of a first idle link operated to effect the seizure of said link when a subscriber calls, and with the relay of the next idle link also maintained operated.

,6. In a telephone system, a cross-bar switch, lines terminating in said switch, links terminating in said switch, means for establishing a connection from any calling line to any other line through an idle link, an allotter for said links for allotting succeeding idle links for use by calling subscribers in the establishing of connections, said allotter including a single relay for each link with two of said relays always operated if more than one link is idle.

'7. In a telephone system, a cross-bar switch, lines terminating in said switch, links terminating in said switch, means for establishing a connection from one line to another line through an idle link, means for allotting said links for use in establishing connections between lines comprising a relay for each link, a common starter wire, and means for advancing said starter Wire through operated contacts of said relays to a succeeding idle link when a preceding link is seized by a calling line through said starter wire.

8. In a telephone system, a cross-bar switch, lines terminating in said switch, links terminating in said switch, means for establishing a connection from any calling line to any other line through an idle link, an allotter for said links for allotting succeeding idle links for use by calling subscribers in the establishing of connections, said allotter comprising a common starter wire, a relay'for each link, means for normally maintaining two of said relays operated for the ad vancing of said starter wire from one link to another, and circuit means controlled by said links for releasing a relay in the allotter when its associated link is taken for use and for operating the relay of the second next succeeding link if idle.

9. In a telephone system, a cross-bar switch, two types of subscribers lines terminating in said. switch, links terminating in said switch, trunks terminating in said switch, means for establishing a connection between a calling subscribers line and a called subscribers line of either or both types through a link, means for establishing a connection from a subscribers line of a first type to a trunk, means for establishing a connection from a trunk to a subscribers line of said first type, means for establishing a connection from a subscribers line of a second type to a trunk under control of the subscriber of a line of the first type, means for establishing a connection from a trunk to a subscribers line of the second type under control of a subscriber of a line of the first type.

10. In a telephone system, a cross-bar'switch, two types of subscribers lines terminating in said switch, links terminating in said switch, trunks terminating in said switch, means for establishing a connection between a calling subscribers line and a called subscribers line of either or both types through a link, means for establishing a connection from a subscribers line of the first type to a trunk, means for establishing a connection from a trunk to a subscribers line of said first type, means operative after a connection has been established between a subscribers line of the first type and a subscribers line of the second type over a link for establishing a connection from said subscribers line of the first type to a trunk, establishing a connection between said subscribers line of the second type and said trunk, releasing said subscribers line of the first type from said trunk and releasing said subscribers line of the first type and of the second type from said link.

ii. In a. telephone system, a cross-bar switch, two types of subscribers lines terminating in said switch, links terminating in said switch, trunks terminating in said switch, means for establishing a connection between a calling subscribers line and a called subscribers line of either or both types through a link, means for establishing a connection from a subscribers line of the first type to a trunk, means for establishing a connection from a trunk to a subscribers line of said first type, means operated after the connection has been established from a trunk to a subscribers line of the first type for establishing a connection between a subscribers line of thesecond type and said trunk and for releasing said subscribers line of the first type from said trunk.

12. In a telephone system, a cross-bar switch, two types of subscribers lines terminating in said switch, links terminating in said switch, trunks terminating in said switch, means for establishing a connection between a calling subscribers line and a called subscribers line of either or both types through a link, means for establishing a connection from a subscribers line of the first type to a trunk, means for establishing a connection from a trunk to a subscribers line of said first type, means operative under control of a subscriber of aline of the first type effective after a connection has been established between said subscribers line of the first type and a subscribers line of the second type over a link for establishing a connection from said subscribers line of the first type to a trunk, establishing a connection between said subscribers line of the second type and said trunk, releasing said subscribers line of the first type from said trunk and releasing said subscribers line of the first type and of the second type from said link.

13. In a telephone system, a cross-bar switch, two types of subscribers lines terminating in said switch, links terminating in said switch, trunks terminating in said switch, means for establishing a connection between a calling subscribers line and a called subscribers line of either or both types through a link, means for establishing a connection from a subscribers line of the first type to a trunk, means for establishing a connection from a trunk to a subscribers line of said first type, means operative under control of a subscriber of a line of the first type effective after a connection has been established from a trunk to said subscribers line of the first type for establishing a connection between a subscribers line of the second type and said trunk and releasing said subscribers line of the first type from said trunk.

14. In. a telephone system, a cross-bar switch, subscribers lines terminating in said switch, trunks terminating in said switch, links terminating in said switch, means for establishing a connection between a calling line and a called line through a link, a key for each trunk at each subscribers station, means responsive to the operation of a trunk key of a subscribers station for establishing a connection between said subscribers line and a corresponding trunk through said switch, means operative in response to a calling subscriber replacing his receiver on the switchhook and operating any trunk key for freeing his line from said connection, and means responsive to the calling subscriber hanging up his receiver for releasing said link.

15. In a telephone system, across-bar switch, subscribers stations, a line from each station terminating in'said switch, trunks terminating in said switch, links terminating in said switch, a key for each trunk at each subscribers station, means for establishing a connection between a calling line and a called line through a link, means for releasing said connection control solely over the calling subscribers line, meansfor freeing the called subscribers line from said connection without releasing it operative by the called subscriber replacing his receiver on the switchhook and actuating any one of said trunk keys.

16. In a telephone system, a cross-bar switch, subscribers lines terminating in said switch, trunks terminating in said switch, links terminating-in said switch, means for establishing a connection between two lines through a link, means for establishing a connection between lines and trunks without the aid of a link, means for releasing a connection between two lines under control of the call originating line only, means for freeing the called line from a connection to a calling line without releasing the calling line from the link used in the connection, said means including a part of the means used for establishing a connection from a line to a trunk.

17. In a telephone system, a cross-bar switch, lines terminating in said switch, links terminating in said switch, means for establishing a connection from one calling line to another line through a link, and means for establishing successively to a plurality of called lines a common conference connection from a calling line over a single link and for signaiing over all previously connected called lines each time a succeeding called line is being connected to the conference connection.

WILLIAM M. BEAUMONT.