Patent GB-759631-A (GB)
Title: Improvements relating to automatic exchange systems
Inventor: FLOOD JOHN EDWARD
IPC: H04Q3/00
Filed: 1953-11-20
Abstract: 759,631. Automatic exchange systems. SIEMENS BROS. & CO., Ltd. Nov. 12, 1954 [Nov. 20, 1953], No. 32289/53. Class 40 (4). Cross-bar switches are used in a singlemarker system, like that described in Specification 759,599, primary and secondary basic cross-bars, arranged in units called link-frames, are provided with one common control circuit per frame, each including four electronic stores to store information identifying the inlet, the outlet, and the link involved in a marked path through the frame. The stores comprise cold cathode gas-filled discharge tubes arranged in lock-out circuits so that if more than one path is marked, information concerning only one can be stored. The marker is released as soon as all the necessary stores are set and the cross-bar switches are then operated under the control of the stores. A group of 100 or more lines or trunks is allotted to a link-frame comprising cross-bars PS1-PS10, SS1-SS10 in Fig. 1, and PSA-PSJ, SSA-SSJ in Figs. 3A, 3B, each cross-bar having ten outlets. As in the other Specification, a line circuit LC, Fig. 2, in a calling condition, extends a forward marking on free paths between a primary link-frame PF, in. coming link circuits ILC and register secondary link-frames RSF to all available free registers RG. An allotter enables one register to return a setting signal to operate the stores in the control circuit of each forward marked linkframe involved in a path to the register. The cross-bars operate and the register transmits dialling tone. When the wanted number is dialled, the marker MK applies a back-marking to the wanted line and the marking is extended through link-frames PF, OSF, IF to all the linkframes ISF that have access to the wanted line. The register operates a relay H (only a contact is shown) and transmits a setting signal over the link-frame RSF already operated, to set the stores and to operate the link-frames in one of the free paths terminating in ISF. The marker is released when the stores are set. A supervisory link circuit SLC transmits ringing current to the wanted line and ringing tone to the register which responds by releasing. Relay H falls back and diverts ringing tone to the calling line. In the case of a PBX group, the marker applies a back-marking to each line of the group. The line circuit LCD, Fig. 3A, is the same as that in the previous Specification, and has the same arrangement for indicating a permanent loop by means of a diode V1. In the primary link-frame, Figs. 3A, 3B, all six wires 100, 124, 125, 126, 39, 40 of one link LJJ are shown linking basic cross-bars PSJ, SSJ. The common control of the link-frame includes four stores ES1-ES4 controlling sets of relays KD, KC, KB, KA respectively. When cross-points are to be operated to connect a link LJJ, the identities of the primary and secondary columns are stored in ES4, ES1. The identities of the primary and secondary cross-bars PSJ, SSJ are stored in ES3, ES2. Select magnets SMP, SMS individual to the link pull up together over contacts of relays KB, KC and hold magnets HMP and HMS pull up later over contacts of relays KA, KB and KC, KD. In effect, stores ES4, ES3 and ES2, ES1 identify the inlet and the outlet and stores ES3, ES2 identify the link. The pulse highways (dotted lines) Fig. 3A, are individual to the basic cross-bar PSJ. Forward and backward markings are extended respectively to leads FM and BM through pulse multiplex links MX1, MX2, gates 17, 18 and pulse lengtheners L1, L2, individual to the cross-bar PSJ. The markings are blocked by gates I1, I4 and I3, I6 under the control of the P-wire if the link is busy. They are also blocked by gates I2, I5 if store ES1 is off-normal. Forward marking pulses from MX1 may be blocked in gate 17 by a backward marking on wire 43 from the marker or by busy pulses from MX3. When a setting signal is returned on wire 30 individual to a trunk it is applied through isolating gates G8, G9 to stores ES1, ES2 which operate. The setting signal is repeated over lead 35 to store ES3 which responds only if the signal coincides in gate G1 with either a forward or a backward marking on the leads 39, 40. The signal is repeated over lead 38 to open gate G2 which then accepts pulses identifying the calling line. When set, store ES4 signals the marker, over differentiating circuit B1, that all the controls are set. Relay RR, which pulls up before hold magnet HMP, falls back when HMP locks to the P-wire and a device E1 then returns the stores to normal by momentarily disconnecting H.T. from wire 19. The condition of the store ES4 is signalled to the marker over lead 44 when a back-marking is applied through gate 18 and pulse lengthener L2 to gate G3. When a backmarking is applied by the marker over wire 43, pulse lengthener L3 produces a number obtainable condition on lead 45 to signify to the marker that the number called is not dead. Multiplexes MX1-MX3, pulse lengtheners L1-L3, gates I1-I8, &c. are substantially the same as corresponding elements in the previous Specification. Gate 12 (or 15) is combined with an amplifier FMA (or BMA) in one circuit, Fig. 12. A positive marking on lead 24 is transmitted through double-diode V16 and cathode follower V17 so long as there is no inhibiting potential on wire 41. Normally, the left-hand triode of V18 conducts, the right-hand triode is cut off and the grid potential of V17 is not affected. A positive marking on wire 24 increases the anode current of the left-hand triode of V16, cuts off the right-hand triode and provides a positive signal on wire 26. The potential on 26 is limited to a range from ground to +50 volts by rectifiers MR26, MR27. An inhibiting signal on wire 41 makes the right-hand triode of V18 conduct and lowers the grid potential of V17. In the device E1, condenser C13, Fig. 14, changes to 100 volts when relay RR operates. On release, gas discharge tube V19 strikes and extinguishes shortly after. Relay X operates while V19 conducts, to disconnect the 100 volts H.T. from wire 19. A second tube V20 is normally conductive. When V19 strikes the negative pulse transmitted through condensers C14, C15 extinguishes V20 until the effect of the pulse dies away. Tube V19 is extinguished, when V20 strikes again on recovery. The store ES1 comprises ten gas discharge tubes 1V21-10V21, Fig. 15, and ten relays 1KD-10KD. The tubes have a common anode resistor R68 so that only one can conduct. The grid of a tube such as 1V21 is connected through isolating rectifier MR29AMR29B(G8) to the setting wires 30 of the ten trunks connected to column 1 of the ten basic secondary cross-bars SSA-SSJ. When a tube strikes, in response to a setting signal, the potential on wire 41 drops to block gates I2, I5, Fig. 3B. Store ES2 comprises tubes 1V22- 10V22, Fig. 15, and relays 1KC-10KC in a similar arrangement in which each tube represents a basic secondary switch. Both stores are restored when the H.T. on wire 19 is interrupted. Store ES3 comprises ten gas tubes 1V24- 10V24, Fig. 16, and ten relays 1KB-10KB associated with 100 gates MR31A, MR32A to MR31K, MR32K (G1) each individual to a link and 10 gates 1V23 to 10V23 (G10) each individual to a secondary basic switch. A 50-volt marking on lead 36 from a marked link LJJ does not strike tube 1V24 identifying the crossbar PSJ until a setting signal on 35 strikes 1V23 (G10) to provide a circuit through MR32A by blocking MR31A. The tubes are supplied with H.T. from wire 19 through common anode resistors. Store ES4 comprises a number of tubes 1V25, Fig. 17, one for each primary column or line. Each tube is connected to the common pulse highway 18 by a coincidence gate comprising rectifiers IMR33-IMR35 marked by cyclic pulses on terminal IPT in a time position characteristic of the line the tube represents. When a pulse on the highway coincides with a marking pulse, tube IV25 strikes and relay IKA operates. Triode V26, normally conductive, is cut off and the potential on wire 21 drops to ground to signal the marker that the controls are set and to lower the priming potential on all tubes IV25. The common anode resistor R86 ensures that only one tube IV25 conducts. The gate G3 comprises a pentode V27, Fig. 19, which is normally biased to cut-off but responds to a rise in grid potential on wire 23 providing that store ES4 is not busy and does not in consequence suppress the pentode by lowering the potential on wire 21. A drop in potential on wire 44 signals the marker that ES4 is not busy. The intermediate register secondary and outgoing secondary link frames IF, RSF, OSF are substantially the same except that RSF has to provide 8 wires for each call. In the intermediate frame IF, Figs. 20A, 20B elements corresponding wholly to elements of Figs. 3A, 3B bear the same references with a suffix W. There are not forward marking facilities. A backward marking on wire 127 is extended over all free links available to primary basic cross-bar PSJW to outgoing wires 29W substantially as in the primary link frame, but the circuit includes an amplifier BMA2 and an isolating rectifier G15 and is blocked at a gate 19 if the store ES4A is off-normal. Store ES1A is like ES1, Fig. 3B, except that the lead 41 is omitted. A setting signal on wire 30W sets stores ES1A, ES2W as before and is extended to store ES3W in which the back-marked basic primary switch is identified by a marking wire 40W and a gate G1W individual to the link and to store ES4A in which the column is identified by wire 127 individual to the trunk. The setting signal is extended over wire 187 when both stores ES4A, ES3W are set to control gate G14. When store ES4A is off-normal, a controlset signal is transmitted to the marker through a differentiating circuit E2 and a wire 185. The store ES4A comprises cold cathode tubes 1V29- 10V29, Fig. 21, and relays 1KAW-10KAW. Ten further tubes 1V28-10V28 constitute ten pairs of gates G12/G30, each pair being individual to a