Patent GB-468722-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M3/523
Filed: 1936-03-16
Abstract: 468,722. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., HENSLER, B. A., and HUMPHRIES, H. E. March 16, 1936, No. 7884. Addition to 412,302. [Class 40 (iv)] In distributing arrangements for connecting calls to subsequent circuits in order of arrival if a subsequent circuit is not immediately available, the distributers being set by calls to positions dependent on the order of arrival so as to form a queue, each call has associated with it a timing device, e.g. a condenser, which is continuously changing its condition during the waiting period, the attainment of a particular condition serving to indicate that a predetermined period has elapsed. The invention is an improvement in the arrangements for distributing calls to operators described in the parent Specification, but the queue-forming and controlling circuits are similar to those described in Specification 439,318 except that the queue outlets occur first in the banks of the distributers and that the present timing arrangements are more precise than the time pulse cycle described therein. The distributers, Fig.2, wait on the queue outlets to which they are set until a connecting circuit is available, the queue outlets leading to wires Tl .. T4, Fig. 3, being seized in rotation so that relays A .. D connected thereto connect charging circuits for condensers QA.. QD. The position of the head of the queue is determined by switch RQ which takes one step each time a call leaves the queue and connects the condenser corresponding to the head of the queue to the control grid of a common pentode VA but immediately before this connection, the control grid is temporarily connected to a predetermined potential so that anode relay AN is energized to a predetermined extent. When the condenser charge reaches a particular value, the anode relay falls back and serves to bring in operators at omnibus positions to deal with the calls exclusively or otherwise. The present arrangements may be applied to the both-way line circuit described in Specification 443,220. Incoming line circuit, Fig. 1. Line relay L on operation makes an initial circuit for line switch magnet DM which thereupon hunts until stopped by high-speed relay T energizing over both windings in series with a rectifier to prevent operation by booster battery. Switching relay H operates, releases Land shunts T which prepares the homing circuit. If the hunt is unsuccessful, the switch remains on its last contacts until a 3-second pulse on PW causes the switch to hunt again, these operations being repeated if necessary. Call distribution under normal demand conditions. The distributers which have two sets of staggered wipers driven by a motor controlled by latch magnet LM, have an overflow contact in the first position followed by 4 queue-forming contacts and a control contact all of which are passed if there is a free assigned circuit. On operation of line relay L followed by B, latch magnet LM is operated and when an assigned circuit is reached, T pulls up from ground at en1, Fig. 3, over the S-wire of the assigned circuit, distributer wiper 5 or 6 (wiper switching occurs on the last contact of wiper 7), T(i) and (ii) in series, and wire P. Relay S being unshunted pulls up and operates switching relay SS and both lock. Ringing tone from RS which was placed on the calling line by B is now removed, B is released and the line switch held by SS under joint control of calling party and operator. If the calling line is not a coin-box line, wire CO is not grounded at the line switch and TC(ii) pulls up to complete the speaking path. The operator may re-ring a calling party by putting battery on the positive wire to operate relay RR. Coin-box lines have wiper P5 of the line switch grounded so that TC(ii) does not operate under the condition described in the preceding paragraph and the operator receives tone from DT which she cuts off by operating TC(i) over the -ve wire. Failure of distributer to find assigned circuit. Relay T stops the distributer on its penultimate contacts, and LC(i) operates in series when T shunts its own winding (i). LC holds over (ii), prevents S from pulling up and releases T, the homing circuit LM, on1 of the distributer being closed. The wiper switching relay WS is released when the distributer is normal and LC falls back so that the distributer is in condition to hunt again. No assigned circuit, calls queue up. If there is a place in the queue (contacts 2 .. 5) the distributer moves off its first contacts and is stopped by T on the first vacant contact, the queue contacts of wiper 7 being connected to wires T1 .. T4, Fig. 3, leading to a lamp display circuit which connects battery to vacant contacts corresponding contacts of wiper 5 being grounded. S pulls up but SS does not since it is short-circuited over wiper 1. TC pulls up over wiper 3 and opens the queue test circuit over wiper 5. When T and S are subsequently released due to the grounding of the relevant wire T1 .. T4 by the display circuit when a circuit is assigned, the distributer is re-started T pulls up again over the control contacts (6) followed by S and DS(i) which locks over (ii) and makes a fresh test circuit for the distributer independent of wipers 5 and 6, TC being also released and SS still prevented from operating. The relapse of TC releases T and S again and the distributer hunts for the assigned circuit, DS(ii) being held until B falls back when the circuit is found. Lamp display and queue control circuit, Fig. 3. When the queue is empty, switch RQ is in one of the positions 1, 5, 9, and so on so that the distributer is stopped on contact 5 connected to wire T1 and thence over A, RQ2 and 3, to idle battery, this circuit normally being open at contacts of CO when an assigned circuit is available (operator has grounded wire RC). Relay A pulls up, connects battery to the next wire T2 of the queue, grounds wiper RQ4 to operate AC and light a display lamp over wire L1, and starts condenser QA (4 m.f.) charging over high resistance YP and a potentiometer YA, YB in the heater circuit of pentode VA. The ground on wire L1 also operates EN(i) which disables the test circuit over CM, of all the connecting circuits, disconnects the control grid of VA from a normal paralyzing bias over YN and connects it to a predetermined potential so that anode relay AN pulls up. Relay AM is therefore unshunted and further changes the control grid of VA by connecting it to the junction between condenser QA and resistance YP which becomes more negative as the condenser charges up. After the call has been waiting for a predetermined time anode relay AN relapses and operates DC to ground wire OM2 to signal an omnibus operator's position whereby such operator may assist in dealing with queued calls, display of other classes of call at her position being prevented if necessary. When 3 calls are queued up, the grounding of lamp wire L3 over RQ6 operates OM(i) over a cross connection not shown, and this relay locks over (ii) and a cross connection to lamp wire L2 which has been previously grounded. Wire OM2 is grounded, if not already so by DC, to signal an omnibus position. When the queue is full (4 calls), OF(i) operates and closes a circuit from Cl to a meter for stopping the distributers on their 1st (overflow) contacts. Taking a call from the queue. The grounding of wire RC when an assignment is made now operates ST(i) which holds over (ii), makes itself slow releasing and momentarily connects battery to RC to remove the ground therefrom at the position circuit. ST grounds wiper RQ2 to release A and also the test relay of the distributer connected to T1 whereupon the distributer hunts for the assigned circuit. The release of A disconnects the charging circuit of QA and discharges it, and the removal by A of ground on lamp wire L1 releases AC and ST so that back-stroke magnet DM operated by ST is released to step RQ to the next contact which makes wire T2 the head of the queue and moves up the waiting calls on the display circuit so that L1 is again grounded, AC re-operated and the waiting period of the head call on T2 timed by condenser QB and valve VA as previously described. The release of AC had released AM so that anode relay AN was again energized to a predetermined extent before timing the next waiting call. Testing. When there is no queue, switch RQ may be stepped by plugging jack TJ since EN is not operated, OF(ii) being operated to cause distributers to stop on the overflow outlet if there is no assigned circuit. Both-way line circuit, Fig. 4 (not shown). This is a modification of the both-way circuit shown in Fig. 1 of Specification 443,220 providing the night service, transfer and other facilities described with reference to said Fig. 1 but embodying the arrangements described above with reference to Fig. 2 to enable the circuit to work in conjunction with the lamp display and queue controlling circuit shown in Fig. 3. The first outlets of the distributers have access to connecting circuits of the transfer operator's position and are followed by the overflow, queue forming outlets, and outlets to connecting circuits of ordinary operators. The distributer test circuits for the transfer operator's connecting circuits are completed by a relay operated when a transfer operator throws an assignment key.