Patent GB-439318-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M3/523
Filed: 1934-08-29
Abstract: 439,318. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, Westminster, HENSLER, B. A., 45, Adelaide Road, Leyton, PETERS, C. L., 51, Verdant Lane, Catford, both in London, GRINSTED, W. H., Under the Plane, London Lane, Bromley, Kent, and CHRISTIAN, D. A., Morven, Charlton Road, Charlton, London. Aug. 29, 1934, No. 24883. Addition to 412,302. [Class 40 (iv)] Calls are extended in order of arrival by hunting switches which, after an unsuccessful search for a free outlet, are caused to assume a position dependent on the order of arrival. The invention is described with reference to arrangements for forming waiting calls to operators into a queue and differs from the arrangements described in the parent Specification in that (1) the queuing-up positions are at the end of the banks of the hunting switches instead of at the commencement, thereby avoiding testing the queue positions in case of a free connecting circuit, and (2) the switches remain in their original waiting positions until a connecting circuit becomes available, their position in the queue being determined by auxiliary switching apparatus which moves the calls towards the head of the queue when the first waiting call is extended. The system described is a demand system with arrangements to bring in relief operators if the queue exceeds certain numbers or if there is undue delay. Extension of call to operator under normal demand conditions. The calling line JCT is extended by line switch P substantially in known manner to distributer D at which L and B operate and latch magnet LM energizes to start the distributer. Normally a connecting circuit such as CC at one or more positions will be assigned by throwing SPK in the connecting circuit and CA in a circuit common to the connecting circuits of a position, relay SK being thus operated. MN pulls up in series with SL which holds SK and connects battery over BA to bank 4 or 4a of the distributer. When an assigned circuit is reached, ground on a contact of EN (described later) over wiper 3 or 3a connected to test relay T operates this relay to the battery on relay BA. Relay T releases the latch magnet and short-circuits ius upper winding to busy the outlet. If the assigned circuit appears in banks 1a .. 4a, WS operates in series with T over last contacts in banks. 3, 4. WS locks and releases T so that the distributer continues the search in banks 1a .. 4a. In the connecting circuit, BA operates CG (i) in series with MN, and connects AS to wiper 3 or 3a of the distributer but this relay does not operate owing to the presence of rectifier r. Supervisory lamp ASL lights up. At the distributer, T removes the shunt on S which locks up and energizes DS(i) and SS in series so that AS in the connecting circuit now pulls up to extinguish ASL. TCO(i) which has no short-circuit connection over P4 in the case of ordinary lines, completes the speaking circuit prepared by S and SS, and B relapses so that the incoming circuit is held jointly by L and S. Completion of call ; release. When the operator has set up the call she restores SPK, CA and CG, MN, SL, SK fall back. When the calling party clears, L releases AS to light ASL, and the operator releases T in the distributer by operating release key REL. Relay S relapses to release the incoming circuit, and LM permits the distributer to home whereupon SS, DS and TCO relapse. Call-box discrimination. Call-box lines have a short-circuit connection over P4 for TCO(i) to prevent this relay from operating when SS pulls-up, and consequently, the operator receives tone over the speaking wires. TCO(ii) is subsequently operated by ground applied by the operator to the negative wire. Ringing a calling party who has left the line. The ringing key (not shown), in the connecting circuit connects battery to the positive wire to operate RR which applies ringing current. No assigned circuit, calls queue up. The distributer proceeds until it reaches the group of leads ld at the end of bank 4a, and assuming it is to head the queue, T pulls up in series with A, Fig. 2, over 1st contacts of wipers ab3, 4 of the queue controlling switch AB. Relays T and A hold themselves in series, and S pulls up, but SS, DS(i) are short-circuited over bank 1a of the distributer. TCO(ii), however, pulls up over bank 2a, locks over TCO(i), and operates DS(ii) which holds B in case the calling party leaves the line. Relay A is held in a circuit independent of banks ab3, 4, prepares a circuit for display relay B also independent of said banks, and lights lamps 1 of the demand position DOP over ab6, relays AC and EN being operated in parallel therewith. The normal test circuit of the distributers is opened at en1, Fig. 1, so that subsequent calls must take their place in the queue, the distributers used in such calls being connected in turn to relays B ... J which light lamps DOP (2 ... 0) over ab7, 8 and banks ba2 ... 8 of a switch BA stepped synchronously with AB. When the lamp panel has been filled with calls (J operated), succeeding calls are directed to lead OF by battery over meter CM and the first contact in ab5. When an operator assigns a connecting circuit, the closure of key contacts CA2, Fig. 2, energizes CN and ST in series, CN operating very quickly and holding in series with CG(ii) while ST holds over its upper winding. The quickness of operation of CN reduces the chance of simultaneous connection to two operators' positions. Back stroke magnets ABDM and BADM are both energized, synchronism of BA and AB being ensured by SY which is operated to open a self-stepping circuit for BA provided that the two switches are in step. Relays A and T are now short-circuited over ab3 so that the consequent relapse of S in the distributer energizes the latch magnet and the distributer goes home where WS(ii) releases and TCO(i) falls back to re-start the distributer which is stopped by the operation of T from ground at tco7 over wiper 4 or 4a to battery on BA in the assigned circuit. The relapse of A extinguishes lamp 1 and releases AC which releases magnets ABDM, BADM so that the switches take a step. Relay ST falls back slowly owing to a short-circuited lower winding. The multiplying between banks ab6-8, ba2-8 and lamps DOP (1-0) is such that when the switches take a step all displayed calls move up one, e.g. the call connected to relay B now becomes the head of the queue by lighting lamp 1. The relapse of A disconnects ground from lead OF so that the distributers held on that lead are re-started. One of them is stopped by the A relay and lamp O is lit, while the rest go on to OF again where they are held by the reoperation of A. Bringing in relief operators. When seven calls are stored, ON operates in parallel with lamp 7, locks in parallel with lamp 6, and grounds a lead AL to bring in a display circuit at a relief position. Similarly after nine calls have been stored, OM operates and energizes AA to connect up the demand display lamps and disconnect the ordinary incoming call lamps at an omnibus position OOP. The ground for operating relay AA is dependent on a relay OOM at the omnibus position similar to OM and which operates if nine incoming calls are waiting at OOP so that the operator thereat is not called to assist in demand working. If the calls are not sufficient in number to bring in a relief, but are for some reason subject to delay, a relief operator is brought in after a predetermined time. For this purpose, each relay A, B, &c., is associated with an individual pair of relays SA, ZA controlled by " S " and " Z " pulses to operate DL which energizes AA to bring relief.