Patent GB-299959-A (GB)
Title: Improvements relating to telephone systems
IPC: H04Q3/42
Filed: 1927-09-21
Abstract: 299,959. Siemens Bros. & Co., Ltd., Christian, D. A., and Long, D. P. Sept. 21, 1927. Semi-automatic exchange systems. - In a system such as that described in Specification 292,331, in which an A-operator at a manual office controls a register-sender at an automatic office by means of code signals over an orderwire, an assignor, comprising two non-homing switches which hunt in succession, selects an idle junction when the order-wire is taken into use, and a link circuit, previously associated with the assignor, hunts for the junction and for an idle register-sender. When the wanted number has been registered, the number of the junction assigned is signalled to the operator who then plugs in to initiate impulse transmission. The assignor may be individual to an order-wire or may be common to order-wires from different offices. When the order-wire is released, the assignor steps to its next terminals. Selecting junction and register sender. The order-wire is seized by the key OW, relays E, F, G providing for a series of fleeting tests as described in Specification 292,331, and if it is available, T connects up the order-wire and locks up in series with TS which busies the order-wire and sends reverse current through T(2) to make T quick to release. LL, Fig. 8, at the incoming end, energizes CB to start the switch OF and removes a short-circuit from CA to mark the order-wire calling. When the switch reaches the order-wire, CA extends the wire A to relays LA, AR, Fig. 2, and energizes CE to disconnect CB and so prevent interference by other order-wires. AR pulls up over A (LA remaining back) and energizes RR in series with CA to start the assignor AP, AQ. If both switches are in their end positions as shown, AP is started in a circuit APM, AQ2, TP.1, AP1, N.1, AQ8, RR.3, this circuit being broken by N as soon as the switch moves and the stepping circuit subsequently depending on the conditions found by the test wiper AP1 and by the wiper AP3 which is in parallel with AP1 and finds ground over contacts such as CA.3 when passing the junctions of non- calling offices. If AP reaches the end of its bank, N falls back, but before it does so a circuit is made for starting AQ over AQM, TQ.1, AQ1, N.2, AP8, AQ8, RR.3. When an idle junction is found, TJ (or TQ) marks it busy and, over AP6 energizes AS, Fig. 3, which marks the junction calling to the links and over LF2 energizes relays SJ, SF in the link that has been previously associated with the order-wire by LF, to start its switches JF, RSF in search of the junction and of an idle register sender respectively. When the junction is reached, K locks up, and when a sender is found KR locks up, marks it busy and energizes KS which energizes KA, KB, JZ. JZ energizes JS, marks the junction busy to the links and over AP7 energizes JL which connects LB to the wire B to operate relay S at the manual office (LB remaining back). S energizes H to release B which cuts off the busy tone which it connected up when OW was first operated. When the assignor is individual to an order-wire, wipers AP3, AQ3 and the apparatus shown in Fig. 8 are omitted, and E is, permanently grounded. Registering number. The digit keys KS connect ground over S(2) to one or more of wires A - - D to operate one or more of relays LA - - LD which transfer their record to storage relays MW - - MZ, CW - - CZ &c. in the register sender, the sequence being looked after by the digit distributor DD which is stepped on by a relay DS operated in parallel with the storage relays. Signalling number of assigned junction; alloting new link. DD on moving to 5, energizes ST, Fig. 4, which energizes PY and CCO. PY starts LF in search of a new link having access to an idle register-sender. Links that have not access to idle register-senders are artificially busied by their relays OB which are energized by GP when relay SB, Fig. 7, which is normally short-circuited over parallel circuits such as COO.3, BG.5, DK, pulls up. CCO switches the wires B - - D from the relays LB - - LD to contacts of relays A - - E. S therefore falls and energizes CO which connects the other end of wires B - - D to lamp relays TA - - TE. CCO also energizes CC and releases DC (energized by TP) and ground over contacts of these relays and AP4 (or AQ4) is connected to one or more of the code sending relays A - - E in accordance with the jumpering of the wires MJC to the bank AP4 (or AQ4) and the junction selected. Of these relays, relay C is of low resistance and will not pull up in series with the high resistance windings 1 of the other relays. The remaining relays however are able to operate over their low resistance windings in series with the windings 1 of the other relays. These relays connect high or low resistance battery to the wire C, the resistance being provided by relay CR, and also to either or both of the wires B, D. Of the code receiving relays, TA - - TE, TA, TB are operated in series over B, TD, TE over D, and TC over C. TC and TE being marginal. CR pulls up on the tranmission of the digit and energizes DR which releases the sending relays and prepares a circuit over AP5 (or AQ5) for re-energizing them in accordance with the units digit. CR then falls and energizes ER which locks itself and DR and releases CC to energize the selected sending relays. At the manual office, P which operates on all codes over the wire C energizes Q which locks up and causes the relapse of P to energize R which switches over to the units relays and locks up. During the units code CR releases DR, ER remaining locked up with CCO. Release of order-wire; allotting new registersender if order-wire is released prematurely and re-seized. On the release of OW, T, TS, H, CO, Q, R and the lamp relays fall back at the manual office, and at the automatic office AR, RR, TP (or TQ), N (or M), JL, CCO and ER fall back. A momentary circuit is made for APM or AQM over AQ2, N.3 or RR.2, M.1. In normal operation, the immediate re-seizure of the order-wire causes a different link and register-sender to be taken into use, LF being stepped on by PY as soon as the full number of digits is registered. In case of premature release and re-seizure of the order-wire, PY has not yet operated and the order-wire is momentarily associated with the off-normal link and register controller just used. In this case, the operation of AS, SJ on the selection of a new junction removes a short circuit from ID and ST, PY pull up and cause LF to allot a new link. Transmission by register-sender. When the operator plugs in, L, LZ, PS in the junction circuit, SY, SX in the link and SS, SR, BG in the register-sender, pull up, and KR, KS, KA, KB in the link fall back SX replaces the bridge across the outgoing talking wires at its own contacts by one at SA1 in the register-sender. SR starts the interrupters I<1>, I<2> and connects them respectively to LLC, CCC. These relays puL up at the first make and remain locked at break in series with LLD, CCD which then connect the interrupters to the loop and the magnet of the sending switch CS respectively. At the first step of the sending switch, SA removes the short circuit from the loop springs and when the switch reaches the terminal marked by the storage relays, SZ stops the digit and releases CCC, CCD. The sending switch races home and SA releases SZ whereupon CCC, CCD pull up again and the next digit is sent, the sender control switch OC moving on after each digit under control of SZ, SA. Normal release of register-sender. C2, in 5, energizes COO which locks itself and BG over their windings 2 and bridge the outgoing wires independently of SS, and SS, SR, the storage relays LLC, LLD, CCC, CCD in the registersender, PY, SY, K in the link, and JZ, JS in the junction circuit fall back. SY unlocks COO and BG whereupon BG falls, sends the switches home and holds COO over a front contact of relay BP until they are normal to keep the registersender busy to the links. Completion and supervision of connection. When JZ switches through, I polarizes D and energizes IR which energizes BF. When the called party replies, D connects LA to the bwire to inform the operator. If the line is busy, I is intermittently released and IR, which follows it, intermittently connects LA to the b-wire to repeat the signal. When the connection is taken down, L, LZ, PS fall back and then I, D, IR, BF. Forced release if operator fails to plug in. KB, when the sender is taken into use, connects TY(2) to ground pulses on S and S locks up and connect SY(2) to ground pulses on Z. If the operator does nob take the junction before the next pulse in Z, SY energizes SX to release KR, KS, KA, KB, PY, K, BG, SY, SX, TY then fall back. The relapse of BG releases the registersender. Fault signals. When impulse sending is about to take place, SR energizes PF which connects PA to one side of a double interrupter ZA, SA. When SA makes, PA locks up and connects PB to the other side of the interrupter. If the springs function correctly, PF is released when CCD and LLD have both pulled up, but if either set fails PB operates, flashes the off-normal lamp SL, gives an alarm and operates COO to restore the sender and mark it busy and release the link. BP, energized in series with the stepping magnets, closes a delayed circuit (not shown) and after an interval contacts MRA energize RA to flash SL and give an alarm. Supervisory lamps; artificial busy keys ; statistical metering. The lamp SL glows when the key SK is pressed if the register-sender is offnormal. Lamp GL indicates that the link is busy. Keys DK in the register-sender and BK in the link restore the apparatus concerned and mark it busy. Relays COO, MM operate meters to show how often a register-sender and an orderwire have been used.