Patent GB-792675-A (GB)
Title: Improvements in or relating to telephone systems
Inventor: HALTON DONALD
IPC: H04M3/523
Filed: 1955-05-24
Abstract: 792,675. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. April 26, 1956 [May 24, 1955], No. 14900/55. Class 40 (4). In a queueing system for exchange line or trunk circuits each circuit is provided with individual equipment for indicating the position in the queue of the associated circuit as determined by equipment common to all the individual equipments and a signal produced by a callanswering condition at a manual position reduces the indication by one in both the common equipment and all the individual equipments and prepares the individual equipment associated with the circuit at the head of the queue for connection to the manual position at which the call-answering condition originated. General arrangement, Fig. 1. The invention is applicable to P.A.B.X. connections to a national network through an operator or to calls to trunk operators. In the embodiment as described with reference to a P.A.B.X. system, each exchange line circuit such as ELC1 is connected to local switching equipment over a path such as LSE and has an individual queue indicator circuit such as QIC1 set by a common queue reference circuit QRC to indicate the queue position which the line circuit is to occupy. The exchange line circuits such as ELC1 are continuously scanned by pulses from cyclic distributer CD. When an exchange line circuit is first scanned on an incoming or outgoing call the scanning pulse is passed over leads PUC and PUG, respectively, to the associated queue indicator circuit such as QIC 1 and the common queue reference circuit QRC. The queue position which is currently available is already indicated by QRC to all QIC's and the pulse on lead PUC operates the corresponding stage in the appropriate QIC. The queue reference circuit QRC comprises a counting circuit stepped forwards or backwards as calls join or leave the queue. It also indicates visually at each manual board position such as 1PC or 2PC the number of calls in the queue. Each position circuit has a single connectanswer key to provide connection automatically to the exchange line circuit at the head of the queue by causing the suite control circuit SCC to extend a pulse over lead PUB to the queue reference circuit and to all queue indicator circuits so that all registrations are reduced by one. At the same time a pulse on lead 1PUE or 2PUE causes that exchange line circuit such as ELC1 already at the head of the queue to be connected to the operative position circuit. The suite control circuit SCC ensures that if two position circuits answer at the same time one takes priority. Detailed circuits. Queue reference circuit QRC and cyclic distributer CD, Figs. 2 and 3. The cyclic distributer has a number of stages such as 1DS, 2DS, NDS equal to the number of exchange line circuits, the stages being arranged in a closed chain. A source of pulses on lead PUD(A) steps the distributer stage-by-stage to pulse the relevant output leads such as 1PUF one-by-one, the pulses on the output leads being applied to the related exchange line circuits. The queue reference circuit, QRC comprises a number of stages 1RS-NRS and ARS which is one greater than the number of queue positions. It incorporates a two-directional chain counter. Each stage includes a. forward count tube such as. 3F and a backward count tube such as 3B, each count tube being associated with a repeater tube such as 3PF or 3PB. The last stage ARS differs in having only a forward count tube AF and a backward pulse repeater APB. When the circuit is first brought into use start tube ST fires to strike the first forward count tube 1F which then extinguishes ST. Tube 1F primes 1PF, 1PB, and 1RO and marks lead 1QB extending to the first stage of all queue indicator circuits. When any exchange line circuit, after seizure, is first scanned by the cyclic distributer it pulses lead PUG to fire PS, Fig. 2, momentarily. Tube PS pulses the trigger electrodes of the forward pulse repeater tubes 1PF-NPF and the relay operating tubes 1RO-NRO. In the present case 1PF and 1RO strike. The former fires momentarily to strike count tube 2F, so extinguishing IF. Tube 1RO lights lamp ILP at each manual position to indicate that one call is awaiting attention. If further exchange line circuits are seized the counter is stepped forwards in like manner so that additional lamps 2LP, 3LP and so on are lighted. When the connect-answer key at a manual position is operated a pulse is applied over lead PUB, Fig. 3, to the triggers of the backward pulse repeaters to fire that tube, say 3PB, primed by the count tube 3B or 3F which is conducting. In the example, 3PB then fires count tube 2B to reduce the queue by 1. Tube 3PB also strikes relay release tube 2RR to extinguish 2RO and lamp 2LP. When the last position in the queue is filled by operation of stage ARS further calls are ineffective upon the queue reference circuit. An overflow queue may be provided for. Queue.indicator circuits, Fig. 4, are provided on the basisof one to each exchange line circuit and each comprises stages 1QS=NQS corre. spending to the number of queue positions to be catered for. According to the number of calls in queue so the reference circuit marks one of leads 1QB-NQB to prime the related tube 1PFA-NPFA. When an exchange line circuit has been seized and scanned a pulse on lead PUC of its individually associated queue indicator circuit fires PD momentarily. The primed tube, say 2PFA, fires momentarily to strike the associated registering tube 2FA to indicate the queue position of the related exchange line circuit. Operation of the connect-answer key at a manual position pulses lead PUB connected to all queue indicator circuits to fire momentarily the primed backward repeat tube, 2PBA in the example, so striking the preceding backward count tube, 1BA in the example, whereby the queue is moved up one step. That queue indicator circuit associated with the exchange line circuit in first queue position fires HA to move to home position. The suite control circuit, Figs. 5 and 6, comprises a counting chain of mutually-extinguishing type with its two stages 1PS, 2PS responsive to pulses from tube CP, Fig. 6, so that tubes 1C, 2C conduct in turn. When the operator at the first manual position 1MPC depresses the connect-answer key relay 1CA energizes followed by relay PC whereupon SO fires to strike SOA, followed by DP at the next pulse on lead PUD(B). Tube DP marks lead PUB to move up the queue one step in the queue reference and queue indicator circuits. DP also strikes SOB which extinguishes SOA. The pulses on lead PUD(B) are retarded slightly by comparison with those on lead PUD(A) so that a line joining the queue shall not interfere with the queue moving up. Tube SOB fires CP after a slight delay, CP pulsing repeaters 1PR and 2PR and tube COO. COO fires to operate relay CO and one of the repeaters fires according to which of stages 1PS or 2PS is operative. Relay CO fires COR after a delay. The fired repeater pulses the corresponding lead 1PU or 2PU. Assuming the former, 1PE and 1PA, fire to operate highspeed relay 1PP. Tube 1PE marks lead 1PUE extending to the queue indicator circuits. Relay 1PP restores PC and 1CA to extinguish COO, SO, DP, SOB, COR, 1PE, 1PA, so releasing CO and 1PP. Potential on lead 1PUE fires PA in all queue indicator circuits, Fig. 4, and in that circuit which has HA conducting, i.e. the circuit in home position, PX and 1P also strike. PX fires HB to extinguish HA. Tube 1P singularizes the associated exchange line circuit ELC which lights a lamp at the particular manual position to indicate whether the call is incoming or outgoing, after which the operator deals with the call. If the operator at the first manual position depresses her key when the suite control circuit is in second position the second repeater 2PR fires to strike 1C and simultaneously pulse the second manual position circuit. This is ineffectual. Relay PC therefore holds up and the suite control circuit switches to first position after a short delay. Recall of operator. If a subscriber already engaged in a call requires the operator he can display a recall signal at the position of the operator who set up the call. The operator then earths lead 1LOR or 2LOR to energize relay 1COR or 2COR and operate relay PCA, whereupon tube CP fires after a short delay. Contacts pca2 open to prevent delivery of a pulse to the queueing circuits, connection being otherwise extended as before.