Patent GB-435398-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/58
Filed: 1934-03-16
Abstract: 435,398. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., WRIGHT, E. P. G., and HARTLEY, G. C., 63, Aldwych, London. March 16, 1934, No. 8350. [Class 40 (iv)] In a rural office, local calls are characterized by a small first digit (2) and calls to or through the main exchange by a group of digits of a considerably larger value (7, 9, 0), and it is arranged that selection of an outgoing junction commences as soon as it has been determined that a call is not local, i.e. as soon as the third impulse is received. The three outgoing digits 7, 9, 0 represent three different types of call, viz. calls to another rural office in the same area, automatically-established calls to exchanges outside the area, and calls to the main-exchange operator, respectively, and after an outgoing junction has been selected a discriminating signal indicative of the type of call is transmitted over the junction, to effect the proper routing of the call at the main exchange. A fourth discriminating signal is transmitted for calls to the operator originated by a coin-box subscriber. Local call. Relays SS, SR operate over the starting lead closing a circuit for relay T which energizes over allotter wiper ds4 and battery over wiper dm4 in the preselected link. Ground is extended over wiper ds1 to operate relays AS, B, DB, FS in the link, and the operation of SO completes a circuit over ds2 for the finder magnet FM. When the calling line is reached, relay P operates over wipers sm8, fm3 and locks in series with LH which in turn locks and shortcircuits P. Relay LH removes a short-circuit over wiper sm9 from relay ON which now operates. Impulses are repeated by relay AS over relay C to magnet DM and when C falls back, relay E operates over wiper dm1 in its second position releasing FS which causes the control switch to advance to its 11th position over dm3. The second digit is also repeated to magnet DM and on the operation of C relay DB is released and a circuit is closed for magnet SM to drive the conversational switch to the beginning of the marked group when relay M operates over wipers sm9, dm2. At the end of the digit relay LC, with or without J according as the digit is odd or even, operates so that the final digit acts directly on magnet SM. Relay LT operates at the end of the digit and connects up P to test the wanted line. If the line is free relay H operates and on the called subscriber's reply FS operates and switches through to relays DS, IS which provide a feed for the called loop. Wanted party busy ; trunk-offering. If the wanted' party is busy, relay G operates to connect up busy-flash lead BFL. A calling toll-operator may break-in by operating relay RR by application of ringing-current or booster-battery to the b-wire. Relay TK is operated to complete a talking connection to the wanted party and when the existing connection is released relay RR is operated again to energize H and release TK. Automatic release of link if calling party fails to hang up. When the called party hangs up, the release of relay DR applies ground to lead TAL so that the next pulse on this lead operates relay ZA which holds over THL. A pulse on ZL then short-circuits LH, disconnecting AS and releasing B, H. Magnet SM operates over contacts on2 to drive the selector to normal when ON energizes over its second (opposing) winding and releases. The finder and control switches also restore to normal. Preselection of link ; statistical metering. The operation of relay ON when a calling line has been found opens the circuit of T which closes a driving circuit for magnet DSM over wiper ds3. When an idle link is found, T operates again and unlocks SR which in turn releases T. If all links are busy, the allotter drives to normal terminals at which SR releases, disconnecting magnet DSM. If a call now comes in, meter OMT is operated in series with DSM by the energization of SS and SR over the start lead. When a link becomes idle, the allotter is stepped on by the closure of backcontact b4 in the idle circuit. Outgoing call. When the third impulse of the first digit is received, relays E, LT operate over wiper dm2 and a driving circuit for magnet SM is completed, the test relay P being connected up over wiper sm8 and contacts au6, ar7, lt7 so that testing occurs in the junction group only. If the digit is 7, relay AU operates over wiper dm1 and a loop over back contacts of LC is connected to the junction to cause the seizure of a main-exchange selector giving access to other rural offices in the area. If the digit is 9, relay SD operates followed by AU so that a temporary ground connection is made to the b-wire of the junction causing the seizure of apparatus for the automatic extension of the call to another area. The operation of SD releases IS which in turn releases SD so that a loop is then completed as before. If the digit is O, relays SD, OG, LC operate, and battery is connected to the b-wire to route the call to the main-exchange operator. If the call is from a coin-box subscriber, the operation of relay CB over finder wiper fm5 causes battery also to be connected to the a-wire to give a distinctive signal to the operator. Operator-hold and recall provisions. If the calling party hangs up on a O-level call, relay AS releases, but DS is held from the operator's board. The subscriber may be recalled by the operation of relay RR by booster-battery or ringing-current over the b-wire. Specification 416,851 is referred to.