Patent GB-759599-A (GB)
Title: Improvements relating to automatic exchange systems
Inventor: FLOOD JOHN EDWARD
IPC: H04Q3/42
Filed: 1953-05-08
Abstract: 759,599. Automatic exchange systems. SIEMENS BROS. & CO., Ltd. May 7, 1954 [May 8, 1953], No. 12889/53. Class 40 (4). A single marker is provided on a 10,000 line exchange using high-speed latch magnet selectors. At each switching stage, groups of selectors with multipled bank contacts have common control circuits in which the identities of the trunks to be interconnected at that stage are stored by means of gas discharge tubes. The marker is released as soon as the common control stores are set and the selectors operate in accordance with the stored information, each selector being driven to find an outlet marked with. alternating current. Line markings are transmitted over time-division-multiplex channels within the common control circuits. Each common control circuit includes a number of sets of storage circuits and of associated equipment, the sets being referred to as master selectors. Ringing tone is transmitted only if a ringer is connected to the called line. Means are provided for indicating a permanent loop or failure of a calling party to clear. The general lay-out is shown in Fig. 1 in which a line circuit LC is multipled to a group of primary selectors PS. The wiper-side trunks 102 of the selectors PS have access to registers RG through incoming link circuits ILC and groups of register secondary selectors, RSS and register tertiary selectors, RTS. A calling line and a called line are interconnected through a primary selector PS (used as a line finder) on incoming secondary selector ISS, on incoming selector IS, a supervisory link circuit SLC, an outgoing secondary selector OSS and a primary selector (used as a final selector) all the selectors being multipled in groups as described. The incoming selectors IS and the incoming secondary selectors ISS are connected in pairs back-to-back. Each selector PS, ISS, IS, OSS has access to 200 trunks on two banks of 100 contacts, a wiper selecting relay being provided to distinguish between the banks. The register secondary and tertiary selectors RSS and RTS each has access to only 100 bank side trunks, the two banks being used for incoming and outgoing signalling. When a line LC assumes a calling condition a forward marking is extended through the common control circuits of free selectors PS, RSS and RTS to every free register RG having access to the calling line. An allotter enables only one register to respond. The register applies a setting signal briefly to a setting wire in section 116 of the trunk 110. The common control of RTS stores the identities of the wiper and bank side trunks to be interconnected and repeats the setting signal to RSS without waiting for the selector to operate. The common control circuits of selectors RSS and PS operate in the same way except that the PS control removes the forward marking and does not extend the setting signal any further. The selectors operate to interconnect the line LC and the register RG. The register operates relay H in the link circuit ILC concerned, transmits dialling tone and grounds the P-wires to hold the connection. When the number is dialled into the register, the marker MK is seized, when free, and the dialled information is transferred thereto. The marker applies a backward marking to the wanted line through the common control of the appropriate group of PS selectors. The marking is extended through the common control circuits of all free selectors PS, OSS, IS and ISS. At the same time, the register transmits a brief setting signal through the outgoing sections of the control circuits of RTS, RSS to that of ISS where the first available marked selector is seized and the setting signal is repeated to selectors IS, OSS, PS. Selectors ISS, RSS are permanently linked by a setting conductor (not shown) in the link SLC. The marker releases as soon as the setting condition has been applied to all the necessary selectors. Ringing current and ringing tone are transmitted from the supervisory link circuit SLC which also applies holding ground to the P-wire. The register releases in response to ringing tone and relay H falls back to interconnect the two parties. Line circuit, Fig. 2. When the loop is closed on line conductors 1, 2 a 10 v. potential is applied to forward marking wire 4. The P-wire is grounded in the register. A busy marking is applied over lead 3A to the common control circuit. The class of service is signalled over the P-wire from a tone source CS. The meter SM responds to a positive marking on the P- wire. Ground is removed from the P-wire if there is a delay in dialling or if the called party hangs up first. The consequent pulse in transformer winding TR(II) strikes gas tube N to give a visible indication and to cut off the forward marking. Primary selectors and common control. Figs. 3A, 3B. Only one set of wipers of a single selector is shown, the second set being connected to leads 64, 65, 66. Forward markings on any of the 200 wires 4 belonging to a group of selectors are repeated by a multiplex MX1 in the corresponding pulse channels on a common highway 5. Similarly, the busy marking leads 3A and the backward marking leads 10 (from the marker) are linked by multiplexes MX3, MX4 to pulse highways 9, 11. A multiplex MX2 transmits signals on 100 setting wires 21 as pulses in 100 channels. As each setting wire corresponds to two lines (one in each contact bank of the selector) each pulse spans two pulses of the other multiplex system. In response to a negative potential on the forward marking wire 4 of a calling line, multiplex MX1 produces a train of pulses on highway 6 if gate I5 is not closed by pulses from MX3 or MX4 indicating that the line is busy or is being called. A pulse lengthener L1 extends the forward marking as a 20 v. negative potential on common wire 22, and on wires 23 and 31 in each free selector (gates I2, I4 open) of the group providing that at least one master selector is free in the common control circuit (gates I1, I3 open). Only one master selector including the storage circuit DS2, SS2 is shown completely. When a setting signal (ground) is returned over setting wires 32, a free master selector (say 2) is seized by an allotter A and the storage circuits SS2, DS2 record respectively the wiper side trunk over which the signal is received and (marked over wires 32, 32B) and the bank-side trunk to which this wiper-side trunk is to be connected. The bank-side trunk is marked by the first pulse received on highway 8B subsequent to the setting of SS2 which is signalled over wires 37. Pulse lengthener L2 opens gate G1 on receipt of the MX2 pulse corresponding to the contacts on which the wiper M is standing when the setting signal is applied. If more than one line is calling, the first pulse is recorded and as the channels on the contact are allocated in the same order, the wiper later moves to the nearest of the contacts concerned. An alternating current characteristic of the master selector 2 is applied to wires 21B and 21 from DS2 to mark the bank side trunk for wiper M. The latch electromagnet LMA operates and a coupling switch CW individual to the masterselector 2 is driven until test relay TA operates over wiper CW1 and wire 35 marking the wiperside trunk. A latch electromagnet LMB then operates and the primary selector is driven until test relay TB is operated by the alternating current marking on wire 21 a filter BPF and an amplifier AD being connected between the relay and wiper CW2. Relay WS then operates, if necessary, over wiper CW4 and locks to the P-wire. With both TA, TB operated, ground is extended from the P-wire over wiper CW5 and gate G3 to SS2 and the master selector is returned to normal. When the line is called, the marker applies a marking to wire 10 and multiplier MX4 produces a pulse train which, if the line is free, is extended through gate 16 to pulse highway 12. Pulse lengthener L3 extends a backward marking over wires 24 and 27 so long as a free master-selector and a free primary selector are available. The pulse train is also fed to wires 8A, 8B, &c., to identify the line in the master-selector allotted when a setting signal is returned from the register. The selector is operated as before. When set, storage circuit DS2 applies a potential to wire 17 a differentiating circuit BE2 transmitting a pulse to the marker to signal that the master selector has been set and that the marker can be released. Multiplexes MX1, MX2, MX3, MX4 comprise rectifier gates controlled cyclically by pulses. Gates I1 to 15 and G2 to G6 all include rectifier arrangements. The gate I5, Fig. 7, comprises three rectifiers MR6, MR7, MR8 to which the pulses on highway 5 are applied. The grid of triode V4 is clamped to ground so long as triode V5 or one of the rectifiers MR6, MR7 is conductive. Rectifier MR7 is fed with " clock " pulses, marking every one of the 200 pulse positions with narrow pulses. A pulse on highway 5 produces a pulse on highway 6 if V5 is not conductive. Triode V5 may be made conductive by pulses or leads 9, 13, 18 or by a negative marking on lead 24. Triode V7 is cut off by a pulse on 18 on a marking on 24 and striker V6 to make V5 conductive. Gate G1, Fig. 11, is a pentode V11 which responds to pulses on the grid from highway 7 only when the suppressor grid potential is raised by pulse lengthener L2 over lead 19. A cathode follower V12 repeats the pulse from the anode of the pentode. Pulse lengthener L2, Fig. 8, comprises a pentode V8 with a delay circuit R24, C14 to prevent the grid potential from recovering in the period between the negative pulses. Pulse lengtheners L1, L3 are modified to respond to positive pulses. The allotter A comprises a discharge tube V14, Fig. 15, for each master selector. A master selector is marked free by 5 v. on lead 37 which maintains a grid/cathode discharge. There is normally no discharge across the main gap as the left-hand triode of the double triode V13 is conductive and