Patent GB-634828-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M3/523
Filed: 1947-11-28
Abstract: 634,828. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and STALLWORTHY, F. A. Nov. 28, 1947, No. 31598. [Class 40 (iv)] In a storing and distributing arrangement in which incoming calls awaiting connection to subsequent circuits are formed into a queue in order of arrival, the various operating circuits of a test relay associated with each distributer are such that an incoming call cannot seize a queue position temporarily vacant due to movement of calls towards the head of the queue and a call failing to be connected to a subsequent circuit after having left the queue has priority of re-entry to the queue over calls waiting in an overflow position. The distributers and the timing arrangements are similar to those described in Specification 468,722. Each distributer has two sets of staggered wipers driven by a motor controlled by a magnet MU, Fig. 1, the first contacts serving as an overflow position and being followed by twenty queue contacts. Normal distribution of incoming calls. On a distributer being seized by an incoming call, line relay L and guard relay B pull up to connect trunk busy tone to the incoming private wire and to operate the magnet MU. Providing there are no other calls in the queue, the distributer is stopped on the twentieth queue contacts by the removal of the short-circuit on the winding I of relay S due to the operation of the test relay TA over the circuit from battery connected in parallel with the first queue relay A, Fig. 2, to wiper 7, and over wiper 5 to an earthed chain of back contacts of the queue relays A ... W. Relay DC operates over its upper winding and wiper 3, and DD follows to send interrupted ringing tone to the caller. The upper or high resistance winding of the test relay is short-circuited and the queue relay A pulls up in series with the 'lower winding to break and make the test circuits for the first and second queue positions respectively, and to operate relays LA, EN, the former lighting a lamp at an operator's position and the latter causing a pentode valve TV to conduct. Anode relay AN pulls up, followed by relay AM and the control grid is connected to a circuit for charging a timing condenser QC, this circuit having been completed by the operation of DC. Succeeding calls are queued in a similar manner. Excessive inflow of calls. The distributer seizing the last queue position stops on the first queue contacts and queue relay W pulls up followed by relay LK, which controls a lamp indicating the full queue condition, and relay OF, which actuates an overflow meter OM, connects intermittent earth to an overflow duration meter OTM and connects batteries to the common leads OPB, OFB. The distributers seized by further incoming calls are prevented from rotating by the immediate operation of the test relay TA from the battery on lead OFB over the overflow contact of wiper T. Relay S operates, and, except in the case of distributers associated with two.wire trunks which distributers have the overflow contact of wiper 3 disconnected, relay LC energizes in series with winding II of relay S in a circuit completed over wiper 3, to send busy tone to the caller and to hold the distributer on the overflow contact until the caller hangs up. Assignment of subsequent circuit. The operator earths lead AST, and relay ST operates and holds, removes the starting earth and disconnects the battery in parallel with queue relay A. The test relay TA of the distributer at the head of the queue cannot hold in series with a queue relay and falls back. Relay S releases, and the distributer hunts for the assigned connecting circuit which is marked by battery on the outgoing private wire p. If the assigned circuit is connected to the bank of contacts associated with the odd-numbered wipers the distributer is stopped in the required position by operation of relay TA. Relays S, H, HA pull up in turn to earth the supervisory wire s, extend the line connections and remove the interrupted ringing tone from the incoming line. If the distributer is one that cannot be taken into use by a call emanating from a call office, relay TC operates over the connection shown in dotted lines and the call is switched through. If the assigned circuit is connected to the bank of contacts associated with the evennumbered wipers, test relay TA pulls up in series with wiper switching relay WS over the last contact of the first bank, whereupon the distributer restarts to hunt over the bank of the even-numbered wipers. Should the distributer fail to find the assigned circuit it is stopped on the penultimate contacts by the operation of the test relay TA. Relay LC pulls up and the distributer rotates to the overflow position, whereon the actuation of the off-normal contacts ON1, ON2 releases the magnet MU and relays WS, TA, LC and the distributer hunts afresh for a vacant queue position. Should there be no vacant queue position the distributer is held in the overflow position by the operation of the test relay TA until battery is removed from lead OPB as described below. Call office calls. In distributers that may be taken into use by call office calls, the dotted line connection mentioned above is not provided. When the distributer is switched to the assigned circuit, number unobtainable tone from lead NUT is sent over the negative wire as an indication to the operator, who switches through by applying earth to the negative wire and thus operating relay TC. Release. The release of relays L, B when the caller hangs up removes earth from the supervisory wire and lights a lamp at the operator's position. The operator may re-ring the caller by connecting battery to the positive wire to operate ringing relay RR. When the operator disconnects the outgoing circuit, general release occurs, connected calls being metered over wire m and calls failing to enter the queue being metered over wire bm. Operation of queue control circuits. On the distributer at the head of the queue moving to search for an assigned circuit, queue relay A releases, followed by relays ST, AM, AN and FE, if operated. The removal of battery from the penultimate queue contacts causes the distributer in the second queue position to step to the head of the queue. The other queued distributers then successively move to the next position. Following the re-operation of A, relays AN and AM pull up in turn, and the control grid is connected to the charged condenser QC. If the time this distributer is held in the queue is such that the charge on the condenser exceeds the predetermined value above which relay AN cannot hold, AN releases and completes a circuit for delay relay FE, and lamps are flashed at the operator's and supervisor's positions, and the operating circuit for overflow relay OF is switched to include keys KTA, KTB. The latter, when thrown, connect the winding of relay OF to earth over the make contacts of the 3rd and 7th queue relays, respectively, and should either of these relays be up, overflow relay OF operates. Keys KNA, KNB are connected to make contacts of the 15th and 7th queue relays, respectively, and, when thrown, restrict the queue to 15 or 7 calls independently of the timing arrangements. When, owing to the release of the queue relays or of the delay relay FE or the resetting of the keys, relay OF falls back, battery is removed from lead OPB, thus allowing distributers that returned to the overflow position after release from the queue to hunt for the vacant queue position before other waiting distributers, and the circuit of slow-release relay OP is opened, which then removes battery from lead OFB. When the queue is empty, the operator may assign a subsequent circuit by operating relay ST and connecting battery to the wire p and earth over a back contact of relay EN to the supervisory wire s of the subsequent circuit. A hunting distributer will then pass all the queue positions to the assigned circuit without any delay. Specification 634,842 also is referred to.