Patent GB-443220-A (GB)
Title: Improvements relating to telephone systems
IPC: H04Q3/00
Filed: 1934-08-22
Abstract: 443,220. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, Westminster, and HENSLER, B. A., 45, Adelaide Road, Leyton, London. Aug. 22, 1934, No. 24211. [Class 40 (iv)] In a system using register-senders, the conversational switches are set by markings applied by devices associated with the switches and responsive to code digits from the sender, the code responsive device at each switch being disconnected and transmission of the next code digit initiated consequent on the switch finding the marked line or an idle line in the marked group. The numerical portion of the wanted designation and digits for setting switches at an incoming exchange are sent in numerical form. The sender may be signalled to proceed with the next code digit by a fleeting signal such as that described in Specification 422,200 (temporary disconnection of the circuit between switch and sender by the switching relay) or it may be effected by operation of the test relay or a relay dependent thereon, whereas change from code to numerical sending may be effected by a different signal, e.g. of a less fleeting nature or different potential. The code responsive devices form part of common control equipment for the conversational switches and in one case, Fig. 5, two groups of switches of the same rank are associable in common with the same group of control circuits. An outgoing switch, Fig. 4, is responsive to two code digits, the first of which sets an auxiliary switch which together with the setting of the responsive device to the second digit effects a marking. This conversational switch may hunt in a marked group if it receives a particular second digit. The invention is described with reference to a system for setting up long distance calls by operators, the system comprising queuing up of incoming calls, automatic insertion of repeaters and gain control thereof, and storage facilities for outgoing calls. The beforementioned switch, Fig. 5, is used for re-connecting to the calling party. Distributing calls to operators. The distributer, Fig. 1, normally hunts for an assigned connecting circuit such as Fig. 2, but if there is no assigned circuit, waiting calls are queued up on a lamp display unit in order of arrival substantially in the manner described in Specification 439,318. Incoming ringing current passes to circuit RRW in which a responding device connects ground to STW to operate start relay ST which energizes latch magnet LM. It will be assumed that an assigned circuit is available over the even numbered wipers thus requiring operation of WS. The distributer rotates to last contacts where ground on wiper 5 operates T, whereupon the switch stops and WS pulls up over (i) and locks over (ii), while T falls back and re-starts the switch. The assigned circuit has ground on wire N as will be seen later, and when the switch reaches it, T again pulls up to battery on wire P in the connecting circuit. The removal of the shunt on S permits this relay to energize DT and SS whereupon the speaking circuit is switched through and start relay ST relapses, a signal over resistance R1 being sent forward over wiper 6 to indicate the nature of the calling trunk for controlling repeater connection. Relay Z is connected to wire STW to respond to a re-ring if required. In such a case Z locks and connects intermittent ground from IE to wire N to flash the supervisory lamp of the operator who, on throwing her speaking key, reduces the resistance on wire N so that SY pulls up and releases Z. Night service and delayed calls. If the night key NSK is thrown, a call operates TF instead of ST, whereupon lamp CL at a transfer position lights up and the transfer operator throws key ANK individual to the calling circuit. Relay AN pulls up, extinguishes CL, and operates WS and ST, whereupon TF falls back. The assigned circuit at the transfer position is connected to the even-numbered wipers of the distributer and the test circuit from wire N is now completed over wiper 8b and PS. Relay TF can also be energized by an operator who may be unable to deal with a call which has reached her. In this case, the operation of AN by the transfer operator releases T which shunts down S and the latchmagnet is energized so that the distributer goes to normal. SS then relapses and ST pulls up so that the distributer hunts for the transfer operator's connecting circuit. Fault alarm. Whenever latch magnet LM is operated, RA connects up a delayed alarm relay, flashes lamp ORL, and opens wire PO to guard against a call in the other direction (see later). Connecting circuit, Fig. 2. This circuit, except that it may have a repeater inserted, and the common position circuit connected to the leads at the bottom of Fig. 2, are generally similar to those described in Specification 401,394 only the relevant or modified features being described herein. When an operator is free to take up a call, she throws listening key SP to operate SK which splits the connecting circuit, connects the incoming and outgoing sides thereof to the position circuit over leads at the bottom of Fig. 2, operates SL and MN in series, and shunts its own upper winding to prevent operation of SK relays in other connecting circuits, SL continuing to connect ground to SK (lower) independently of the listening key. The connect answer key CA is now thrown and it will be seen that the test circuit for the distributer is completed from battery over B to wire P at one end and ground on wire EN (see Specification 439,318) connected to wire N at the other end. The test circuit for the transfer position would be completed over wire PS instead of P. Relay B operates over the test circuit and is followed by BA slowly, but in the meantime NA and NC are connected to the N wire and receive the repeater connecting signal whereupon NA or NA and NC lock up. CG operates in series with previously energized relay SL and brings about the release of a call from the queue if there is one, and relay BA connects the supervisory relay AS to the N wire. The speaking key SK being thrown, the operator ascertains the wanted number and throws the send call key SCK which by contacts not shown starts the sender connecting switch SCS, Fig. 6, and operates K in the first selector, Fig. 3. The operator keys up the number and presses the start key ST which operates SD and SE, whereupon the four outgoing +, -, NP, NN wires are connected through to the sender which transmits the digits in code. If the call is to be set up by a reverting selector, as described later, the send answer key SAK is operated instead of SCK and the sender will be connected to the answering end of the connecting circuit. When the connection has been set up and the speaking key restored, SL, SK, SD, SE relapse to connect up the speaking path if a repeater is not required. Supervisory relay CS is operated by ground returned over the outgoing circuit, extinguishes the supervisory lamp CSL and starts the timing device MR. Insertion of repeater. It has been seen that NA alone (no repeater), or with NC (repeater required), is operated in accordance with a signal from the incoming trunk circuit. Similarly, NB alone or with ND is operated from the outgoing trunk circuit. If either NC or ND is operated, start relay ST of a repeater connecting switch operates latch magnet LM, closes the heater circuits of the valves, and connects relay T to the test bank which is marked over RC. When the connecting circuit is found, T stops the switch and removes a shunt on H which pulls up in series with the inert latch magnet, extends a chain start-circuit to the next repeater and connects the gain control relays GA, GB to wiper 7. Relay GA operates in any case and HA pulls up to switch in the repeater and balancing networks, whereas GB operates only if both the incoming and outgoing gain signalling relays NC, ND are operated to cut out a resistance in the gain control circuit. GA and GB control connections to gain control potentiometers (not shown) giving a choice of two values of gain. Relay T also energizes RC which re-operates SD to split the connecting circuit, monitoring connections being extended to key MON. Register sender, Fig. 6. Six relay registers AW .. AZ, ... FW .. FZ are provided of which only the first three are shown, the last three being connected similarly to CW .. CZ to successive contacts of distributer DD, and the first two being adapted to be used twice so as to provide for 8 digits. Sender SS is used for transmitting numerical impulses after the connection has been extended out of the trunk exchange or to the local switches and as at least one code digit is required to do this, the sender is not marked for the first digit, BW .. BZ provides markings for the 2nd and 8th digits, AW .. AZ is used for the 7th, and the remaining registers are taken in turn. The marking contact - trees of registers CW .. CZ, ... FW .. FZ are not shown. An operator requiring a sender throws key SCK, Fig. 2 (or SAK for a reverting call), and thus grounds wire IN, in a manner not shown, connected to start relay ST of the motordriven finder SCS. When the position circuit is found, battery on wire P operates T to remove the shunt from H which switches wires NP, NN, +, -, incoming from the key-strip to the distributer wipers DD3 .. 6. Relay HA also pulls up to prepare various circuits and connect the chain start circuit to the next finder over OUT. The ground pulses from the key strip for each of the first six digits operate combinations of the register relays over their left-hand windings in series with stepping relay DS which energizes the backstroke magnet DDM of the distributer, DS, DDM relapsing at the end of each digit to step the distributer and the register relays locking over their right-hand windings. A particular 1st digit operates SD(i) whereas a particular combination of 1st and 2nd digits operates SD(i) and ED(i) in series. These relays lock up o