Patent GB-484647-A (GB)
Title: Improvements in or relating to automatic hunting switch or like circuit arrangements for use for example in telephone systems
IPC: H04Q3/00
Filed: 1937-08-21
Abstract: 484,647. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. (Kozma, L.) Aug. 21, 1937, No. 22968. [Class 40 (iv)] In a system in which alternating current is used for marking purposes and in which lines are connected individually to a marking multiple and are also connected in groups to common points for group marking or for control of a group starting circuit, the connections to the common points are made through segregating devices which prevent the alternating current on one of the lines from passing back to the other lines of the group. In one arrangement, Fig. 1, the lines IL are connected directly to the bank of one finder switch IM and are connected together in groups through condensers C to common points in the banks of a second finder IF, the condensers being of such value that they will pass the highfrequency employed for group marking but the low-frequency employed for individual marking will not pass appreciably through two condensers in series from one line to another. In another arrangement, Fig. 2, the individual lines are connected through rectifier networks connected in parallel to the primary winding of a transformer T, this arrangement allowing alternating current of any frequency to pass from any line to the transformer but not allowing passage back to any other line. The invention is described with reference to two systems, described in detail in succeeding paragraphs, for identifying calling lines for the purpose of transmitting the calling party's number to an automatic ticketing machine. In the first system, Figs. 5 and 6, the 10000 lines of the exchange are multipled in groups of 20 through individual condensers 1 .. 10 to the terminals of a 10-wiper 50-point switch IM. The ten wipers are also multipled through rectifier networks R1 .. R10 to a common point for controlling the selection of the 200-line group. The determination of the 20-line group is effected by successive testing of the wipers imm 1 .. imm10 and the individual line is identified by a final selector, normally employed for incoming connections and taken into use for line-identifying purposes by a hunting switch IF. The final selector is of the 200-point power-driven rotary type sending back reverting-impulses which effect the recording of group and units digits on switches MT, MU. In the second system, Figs. 7-10, in which toll calls are made via a cord circuit CC at a toll exchange and an outgoing junction OGJC with which are associated a ticketing machine TM and a control circuit TCC, the digits denoting the calling number are transmitted to the toll exchange over an auxiliary junction line JW3. The line-identifying equipment comprises a 50-point switch FA which finds the 200-line group, and fourwiper 50-point switches FL each giving access to the 200 lines of one of the groups. First system, Figs. 5 and 6. Operation of start relay Gs energizes relay Gb in series with relay Ot in a free identification-control circuit. (If all circuits in the group controlled by Gb are busy, relay Ng operates due to the non-operation of Gb and extends the start circuit to another group). Relay Vd operates, energizing relays Vc, Do, and is then released slowly. During its operation, 2000-cycle current is connected to transformer DT and if the valve DV is faulty, relay Va energizes on the release of Vd releasing the circuit and flashing lamp BL. If the valve DV is in order, relay Ar in the anode circuit operates and energizes Ok which locks in series with Vb. Magnet IMM operates to drive switch IM in search of the 200-line group including the calling line which is marked by 2000 cycle + 150 cycle current. When the group is reached, the 2000-cycle current passes over one of the rectifier networks R1 ... R10 to transformer DT and relay Ar stops the switch and energizes relay Bt. To avoid double connections, relay Mt is connected up by Bt to make a second (direct-current) test over wiper imm 11 and if two switches have stopped on the same contacts, Mt does not operate and a new circuit is completed by relay Dc for magnet IMM. When Mt operates it locks in series with Md which energizes magnet IFM to search for an idle final selector serving the selected 200-group of subscribers' lines. When this is found, relay Ft operates over wipers imm13, ifm1, ifm3, and relay Fd tests for double connections. Relays Fh, Do, operate disconnecting the tone from transformer DT, and when relay Ar releases, relay Af operates and completes a fundamental circuit over relay Os and wiper ifm2 to the b-wire of the final selector. Reverting impulses are sent back to relay Os which steps switch MT until wiper mm3 makes connection to the wiper imm1.. imm10 corresponding to the 20-group containing the calling line. The 2000-cycle current operates relay Ar again to energize relays It, Us and open the fundamental circuit. Relay Us releases Ar and the fundamental circuit is again closed, reverting impulses being sent back and repeated to magnet MUM until relay Ar is operated over lead 3 by the 125- cycle current picked up by the test wiper of the final selector, the circuit including a 125- cycle filter. If the signal persists long enough to ensure that it is the correct tone and not mere potential kicks, relay It releases Ta, and relay Lt operates. Relay Cw energizes over wire 3 in parallel with the subscriber's cut-off relay and holds relay Ot. The digits correspending to the calling number are transmitted in known manner, the first two being fixed exchange digits and the remaining four being determined by the positions of IF, IF and MU jointly, MT, and MU, respectively. If premature release occurs whilst the final selector is hunting for the calling line, switch MU moves to position 21 in which wiper mum2 operates relay Rl to release all operated relays and to energize relay X which interacts in turn with magnets MTM, MUM to restore the register switches to normal. Relay Rl is then short-circuited over wipers mum1, mtm2. Second system, Figs. 7-10. When the wanted number, tariff digits, and type of call have been recorded in the ticketing machine, 600-cycle current is sent back over the third wire of the connection to operate relay S, Fig. 8, in the incoming circuit IJC. Relay SR operates and switch DF hunts for the circuit IJC. When this is reached, relay T is operated over wiper dfm2 by the 600-cycle current and relay TT causes switch JF to hunt for an idle auxiliary junction line JW3. Relay TT also operates relay TS and connects up 600-cycle plus 2000-cycle current which is transmitted through transformer MTR over the junction J in a simplex circuit and thence through transformer LTR to the c-wire at the originating exchange. Relay JS operates earthing the start lead STL for the control circuit ICC, Figs. 9, 10. Relay ST energizes relay STR which in turn operates relay SR to cause the switch SS to move to position 2. Alternating current is transmitted over wipers ssm8, ssm7 to valve circuit VC and if the circuit is in order, relay V operates and energizes SR over wipers ssm3, ssm1 to move switch SS to position 3 in which relay V releases and the switch moves to position 4. Magnet FAM operates over wiper ssm2 and switch FA hunts over wiper fam5 for the marked 200-line group. When this is reached the 2000-cycle current passes via wipers ssm8, ssm7 to operate relay V which energizes relay SD. Relay DT makes a test for double connections over wiper fam7 and if such exists, relay DT opens the circuit of V, and the switch FA continues hunting. If DT does not operate, slow-to-operate relay GS energizes and switch SS moves to position 5 in which finder FB hunts for the position marked by FA. When this is reached, relay T operates and switch SS moves to position 7, in which magnet FLM operates over wiper jam8 to advance the switch FL selected by FA to find the set of four lines including the calling line. When this is reached, relay V operates under control of the 2000-cycle current transmitted over one of the wipers flm1 .. 4 and the corresponding one of wipers fam1 .. 4 and moves switch SS to position 9. The four lines selected by switch FL are successively tested for 600- cycle current in positions 9, 11, 13 and 15 of SS, the valve circuit VC being appropriately tuned by condenser TUC2. If the first line is calling, relays V, LS are operated in position 9 and the switch moves to position 16, and similarly for the other three lines, relay MS, DS or OS is operated in position 11, 13 or 15, respectively. In position 16 relay LFC operates, if no similar relay in another circuit is operated, and moves the switch to position 17, 18, 19 or 20 according to which of the relays LS .. OS is energized. Relay JG operates during this movement and on its release switch FC hunts for the auxiliary line JW3 which is marked by 900-cycle current over ssm10, ssm9, flim1 . . 4, c-wire, junction J, dfm1, jfm1. When this is found, relay V operates energizing JF and moving switch SS to position 21 in which relay LFC is shortcircuited and the switch moves to position 22. Relays SSR, SP operate causing interrupter IS to impulse relay IR and on the first impulse, relay CP operates and sends 750-cycle current over wipers ssm7, ssm8, fcm1 to operate relays T, JSA, Fig. 8. Relay JSA cuts off the marking frequencies and at the end of the 'signal, relay KS operates connecting wire JW3 through to the c-wire of the cord for the transmission of the calling party's number. Three exchange digits, in positions 23-25 of SS, are determined by jumperings between banks ssm6 and sam2 ; the thousands digit, in position 26, by a jumpering between banks fbm1 and sam2; and the remaining digits, in positions 27-29, by connections from banks flm5 .. 0 to points on a resistance PR1, impulses being sent until wiper sam3 connects up a similar amount of resistance PRÀ when differential relay DF releases and through relay DFA releases relay SP. In position 30