Patent GB-550054-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M3/523
Filed: 1941-06-27
Abstract: 550,054. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and LONG, D. P. June 27, 1941, No. 8139. [Class 40 (iv)] In a call storage system in which calls are distributed to several operators' positions from a common queue, each of the circuits over which calls arrive is provided with a hunting switch DA (or with several associated switches DA, DB acting as one) and on the arrival of a call this'switch moves off-normal to mark the circuit calling to a number of finders FA one of which has been previously allotted to a switch AS. When the current is found, a queue'relay CA individual to the finder grounds one of a group of wipers equal in number to the maximum number'of places in the queue in a queueing switch RA to indicate to the operators that the queue has another occupant and the allotting switch prepares the next finder. When an operator signals her readiness to extend a call, the switch DA is released from the call finder and hunts for a marked connecting circuit. As each call is called from the queue, the queueing switch moves on until, when there are no more calls its position corresponds with that of the allotter. This alignment is maintained automatically in the absence of calls. Forming queue.-When a. call arrives over the circuit shown in Figs 1, 2, relays L, B, G, T, TA and N pull up, ring-back tone is sent and switch DA is stepped off-normal to operate the starting relay SF in the allotter circuit shown in Figs. 3, 4 and apply a marking potential over wire B to the terminals of the circuit on the finders such as FA. Relay T is now held, according as the circuit is an odd or even one, in series with PA or PB which lights lamps (not shown) over LA to indicate a waiting call to the operators. A meter WCM in series with PA and PB indicates the number of waiting calls. The previously allotted call-finder hunts for the calling circuit under control of a common test relay TDA which, on operating to stop the finder, energizes TQ in parallel with the queueing relay CA individual to the finder. TQ energizes the allotted magnet and the queueing relay energizes AC over one of the banks ra 6 .. rb8 of the queuing switches, there being one bank for each queue position. AC energizes EN which disables the automatic aligning function. CA &c. shunts out TA whereupon T, DA, TQ fall back and the reverse-drive allotter moves on. If another circuit is calling the newly allotted finder hunts for it, the next queueing relay is operated and an additional lamp at each operator position is lit over LB. When the queue is full, DF is operated and disconnects SF from wire A to prevent further attempts to enter it. Extending calls from queue.-When an operator is ready, she operates a key or inserts a plug which grounds wire PCS. ST pulls up and locks and sends a signal to cause the disconnection of ground from PCS. Ground is connected for an instant terminated bv the sluggish operation of CR to wire C to shunt out T, Fig. 2, in the circuit connected over wiper ra4 of the queue switch and start the switch DA therein in search of the allocated connecting circuit. If DA fails to find the circuit, the search is taken over by DB. When the circuit is found, T, TA pull up to stop the switch and extend the talking and test wires. SA operates over the latter and is followed by SS, TD to complete the talking circuit. On the operation of CR, CA falls and the driving magnet of the queue switch RA is operated. AC, ST, CR, EN fall and the switch moves its wipers and is followed up by RB. The second call thus becomes head of the queue and AC, EN reoperate, the position being indicated to the operators by the lamps energized over LA, LB &c. Premature release.-Relays L, B and G fall but T and N are held and the incoming circuit continues to be marked busy. When an operator answers the abandoned call, ST energizes R which locks and energizes S. The switch DA moves on but. since its test circuit is not complete, moves to its home position. On the release of CA, AC, ST, CR and EN fall back and the queue switch takes a step. On the release of ST, relays R, S fall in succession giving an impulse to ST which locks up and causes the next call to be extended without a further signal from the operator. Normal release.-On the relapse of relays L, B the upper winding of SA is shunted to reduce the resistance of the wire S to signal the operator. When she clears, SA, T, SS fall and the incoming P wire is unguarded temporarily to enable previous switches to release, the guard being replaced on the relapse of G until the switches DB, DA have been restored. Ringing back.-After the subscriber has cleared, he can be recalled by connection of battery to wire T to operate RR which connects up ringing current. Coin box calls.-These are identified by a connection of the left-hand winding of TD to a tone source, the relay transferring a signal by transformer action when SS pulls up and the operation of TD being deferred until the operator applies ground to the wire R. Extending calls direct; irregular working.-If a connecting circuit is allotted before a queue begins to form, the operation of ST without EN energizes DP and the switches DA, DB thus hunt for the connecting circuit as soon as a call arrives. If the queueing apparatus is defective, a key KEW is operated to prevent the operation of the finder starting relay SF on the arrival of a call and to cause DP to operate instead of ST when an operator signals readiness to deal with a call. As a result, all relays T are released and the switches DA, DB of all waiting circuits hunt for the connecting circuit. When one is successful, DP is released and the switches DA in the other circuits stop on their second terminals. If, during queue working, the switches DA, DB of the circuit called from the queue fail to find the allotted connecting circuit, DB is stopped on its last terminals, energizes TD, which releases T, TA, and then goes.home. DA also goes home, whereupon N is shunted out and releases TD. Conditions are now as when the call arrived and it joins the tail of the queue. When a call joins the queue, relay EN changes the potential of the grid of a valve VA to enable its anode relay AN to operate. Each queue relay completes a charging circuit for an individual condenser QA. AN allows the operation of AM which connects the control grid to a point in the charging circuit associated with the call at the head of the queue. If this circuit is maintained, AN is released in due course and W connects up a flash signal relay to indicate excessive delay. Specification 468,722 is referred to.