Patent GB-465011-A (GB)
Title: Improvements relating to telephone systems
IPC: H04Q3/00
Filed: 1936-02-20
Abstract: 465,011. Automatic exchange systems. SIEMENS BROS & CO., Ltd., and HENSLER, B. A. Feb. 20, 1936, No. 5161. [Class 40 (iv)] If a selector controlled by a common marker hunts unsuccessfully over a marked group it releases the marker and then subsequently, when an outlet becomes free, again takes into use a marker and performs a further hunting operation over the same group, no repetition of the original selecting digits being necessary. The invention is described with reference to a system similar to that described in Specification 443,220 in which a second trunk selector is set by two code digits transmitted from a registersender, the first digit selecting the wanted group and the second determining whether the selector shall hunt over the group or be set to a particular junction, and in the former case whether in the event of all junctions being busy it shall move to a call-storage position and wait for a junction to become free or shall move to its last contacts to give a number-unobtainable signal. Seizure of marker and selection of wanted group. The testing-in circuit from lead P includes contacts on 2, lead 22, relay TZ, contacts mon 2, and relay B. Relays B, TZ, JB, JC operate, the two latter opening the testing-in circuits from all other selectors associated with the same marker, of which there is only one to the group of selectors. Relay JC also closes a circuit over lead 23 for coupling-relay K which in turn operates an auxiliary coupling-relay KA. Relay PF operates slowly and the first digit consisting of battery on one or more of the incoming wires +, -, NP, NN, is recorded on relays AW .. AZ. A circuit is then completed for latch-magnet MLM of the marking switch which hunts for a position in its bank M 1 or M2 marked by relays AW .. AZ, the choice of bank being determined by relay BS controlled by a discriminating signal over lead PP. When the marked position is found, relay P operates energizing PT which releases PF. During its relapse the ground connection to the incoming signalling leads is open to signal to the register-sender that the next digit may be sent. Second digit denoting call-storage and repeated hunting.. In this case, relays AW, AX, followed by GS, are operated and a circuit is completed over lead 28 for the selector latchmagnet SLM. The testing circuit extends from wiper 6 over leads 35, 36 and wipers 7, M5, and if an idle junction is found relay T operates connecting relay HC (i) into the latchmagnet circuit and thereby releasing the magnet. Relay HC releases relay B to initiate the freeing of the common circuit and also converts ground over leads 29, 30 to operate switching relays HA, H. If no idle junction is found, the selector moves to contacts Y connected to a call-storage equipment where relay TB operates over wipers M4, 7, leads 36, 35, to ground on wiper 6. Relay OF operates to release B and the marker and to energize relay HA which switches through the +, -, and S wires, the latter through relay RR. When a junction becomes free, the storage equipment connects interrupted earth to the S wire to signal the operator who by pressing his speaking key causes relay RR to operate. As soon as the marker is free, relay RS operates over lead 32, energizing relays B, JB, JC, PF, RT. The marking switch first hunts under the control of its wiper M3 for the particular selector involved and operates its auxiliary coupling-relay KA. Relay P also operates, energizing PT which completes a new circuit for the latch-magnet MLM to advance the marking switch to the correct marking position as determined by the connection to bank M4 over wiper 7, lead 36, and relay T. The operation of T inserts relay GS (ii) into the driving circuit to de-energize the magnet MLM and to operate GS which completes a driving circuit for the selector latchmagnet as before. Hunting is resumed and terminates as before either in the selection of an idle junction or in connection to call-storage apparatus. Second digit denoting hunting to last contacts. In this case, relays AW, AX, AY, followed by AT, GS, are operated, wiper M4 is disconnected, and if no idle junction is found relay T operates over lead 37, wiper 7, leads 36, 35, wiper 6, and resistance YZ at the last contacts. Number-unobtainable tone is supplied over wipers 1, 2. (The selector also moves to last contacts if an unallotted first digit is sent, by reason of a jumper from bank M5 to terminal TSN.) Second digit denoting selection of a particular junction. For any other combination of relays AW .. AZ than the two referred to above, relay N operates and the selector hunts for a particular junction, the testing circuit including relay T, contacts of relays AW .. AZ, wiper 8, lead 38, wipers M5, 7, lead 36, resistance YC. When this is reached, relay HC operates in the driving circuit energizing relays H, RR (ii). The common circuit is freed as before and on the release of relay K relay RR is connected to test wiper 6. If the junction is busy, RR remains operated and busy-tone BTG is connected to the speaking wires and busy-flash signal LFG to the supervisory wire S. The selector remains on the busy junction until it becomes free when RR releases and relay HA operates to switch through.