Patent GB-710161-A (GB)
Title: Improvements in or relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1952-02-22
Abstract: 710,161. Automatic exchange systems and switches. TELEFONAKTIEBOLAGET L. M. ERICSSON. Feb. 22, 1952 [Feb. 23, 1951], No. 4751/52. Class 40 (4) In a cross-bar system in which a switching centre is connected by a number of junctions to an exchange, a set of control wires common to the junctions extends from the switching centre to the exchange. For incoming calls the exchange marker sets the switching centre marker by marking a combination of the control wires. For outgoing calls a combination of the control wires characterizing the caller is marked to operate registering relays at the exchange which connect up the caller's meter, set the switching centre marker, and find a path consisting of a free junction connectable over a free link to a free registercontroller. Talking current is supplied from the exchange. Two systems are described. In the first, each switching centre has 100 subscribers, one stage of cross-bar switches and an auxiliary current source consisting of an electrolytic condenser charged from the exchange., During conversation only one relay and one operating magnet are operated at the switching centre and these are held due to the remanence of their cores and are released by a current opposite in direction to the operating current. In the second system, each switching centre has 200 subscribers, two switching stages and a separate current source. First system. Outgoing call from switching centre, Figs. 1, 2.-Each of the hundred subscribers of the switching centre is connected to an operating bar of a number of cross-bar switches AK, the selecting bars of which correspond to junctions to the exchange, Figs. 3 to 7. The line relay LR1 of subscriber A1, providing the marker, Fig. 2, is free, operates tens and units relays LR11, AR1, respectively, which disconnect the other relays AR1 ... AR20 and earth a combination of the control wires s5 ... s12 so operating at the exchange registering relays BR5, BR9. Relay BR11 is energized in parallel with the registering .relays and BR12 and CV1 follow. CV1 disconnects the other relays CV2 ... CVn which each correspond to a switching centre connected to the selector stage BK, the selection bars of which correspond to junctions to switching centres and the operating bars of which are connected to incoming or outgoing links such as T1, T3, respectively. Relay BR12 completes test circuits for paths each including a free junction (a, b, c) and a free link (T1) associated with a free register connector (RS1). It is supposed that relay BV1 associated with the switch BK shown, pulls up followed by a selecting magnet BS1 corresponding to the junction a, b, c, and the selecting magnet ES1 of the register connector RS1 which serves the link T1. Circuits are completed over test relays ER1 . . . ERn for free register-controllers and say ER1 disconnects ER2 ... ERn, whereupon the corresponding register controller REG1 by energizing in turn operating magnets EB1, BB1 of the switches RS1, BK, respectively, connects itself to the junction a, b, c. Meanwhile BR10 operated by BR12 connects the positive pole V + of an auxiliary battery BV to the control wires corresponding to energized register relays BR5, BR9 to bring up marker relays AR31, AR35 in the switching centre and completes a circuit over wire b for AF2. Relay AF2 connects up the selecting magnet AS12 pertaining to the junction a, b, c. The marker relays AR31, AR35 release the tens and units relays AR1, AR11 and operate relay AR21 so completing a circuit for the operating magnet AB1 associated with the caller A1. Relays AR40, AF1 pull up and AF2, LR1 and the selecting magnet AS12 fall back. At the exchange BF1 brings up BF3 which breaks the test circuit of the junction a, b, c. When relay BR11, disconnected by BR10, eventually releases the relays and selecting magnets used in connecting the caller to the register-controller REG1 are released. The call is set up over a link SNR2 or SNR1 to subscribers at the exchange or switching centre respectively. Metering.-A cross-bar switch CK has three groups of selecting magnets CS1 ... CS4, CS5 ... CS8, CS9 ... CS12 on which are registered the hundreds, tens, units digits, respectively, of the caller. A1. Relays BR10, BR11, individual to the switching centre shown, energize CS3, and the registering relays BR5, BR9 energize CS8, CS12. The operating bars of the switch CK correspond to the links such as T1 and operating magnet MB1 is energized by the register-controller REG1 in parallel with the operating magnet BB1 of the switch BK. The register-controller REG1 just before releasing operates NR1 which is held from the link circuit, say SNR2, and which connects the calling line to the link circuit. When a metering pulse is reverted over wire d2, relay NR2 locks up to operate relays DR1, GR1. A relay DR1 ... DRm is associated with each link and groups of relays such as DR1 ... DRn, DRk ... m are provided with group relays GR1 ... GRp. The operation of relay DR1 transfers the three digits registered in the switch CK to three groups of relays ER1 ... ER4, TR1 ... TR4, HR1 ... HR4. Relay HR3 energizes a selecting magnet DS2 of a ten by ten crossbar switch DK having ten contacts in each contact set; the contacts being connected to a thousand meters SMA1 for the subscribers at ten switching centres. Relay TR4 energizes operating magnet DB1 and relay ER4 connects the upper winding of NR2 in series with the contact of the operated contact set leading to the caller's meter SMA1. Relay NR2 falls back to release the switch DK. All junctions busy.-Since the selecting magnet AS12 is unoperated, the marker at the switching centre cannot energize AR40. Thus slow-operating relay AB39 is allowed to operate and operating magnet AB1 releases the line relay LB1 and connects the busy tone leads s3, s4. When the caller hangs up the current for AB1 is reversed and all circuits release. Current supply at switching centre.-The operating currents are obtained from an electrolytic condenser AC charged over leads s1, s2 from the exchange battery. Current is required at the switching centre only during the setting up of a connection since, during a connection, relay AF1 and the actuated operating magnet of switch AK are held due to the high remanence of their cores until a reversed current demagnetizes them. Incoming call.-The marker M earths lead VI pertaining to the wanted switching centre. Providing a call is not being set up from the switching centre so that BR11 is back, relays MR1, BR1 connect the control wires s5 ... s12 to the marker M and complete a circuit for BR12, CV1 to operate followed by BR10. Relay BR13 connects the test circuits for free junctions such as to a, b, c, to the test circuits for free outgoing links such as T3. It is supposed that BV1 and the selecting magnet BS1 operate and that the marker M seizes link T3 and energizes operating magnet BB2. Relays BF1, BF3 operate. At the switching centre, relay AF2 energizes the selecting magnet AS12 corresponding to the junction a, b, c, and the marker relays AR31, AR37, AR38 relating to the called party A2 are operated by the exchange marker M, whereupon relay AR21 completes a circuit over lead V2 for the operating magnet AB2 to switch through. Relay AF1 operates. Called party busy.-When the marker relays connect up lead V2, a circuit is completed over wire c of the junction used in the established call for the relay corresponding to relay BF2 associated with that junction, whereupon a contact corresponding to 104 operates a busy relay in the marker M. Release.-When the exchange end releases BF1 falls back. When the switching centre subscriber hangs up providing BF1 is back, BF3 releases and applies potential V+ to wire c whereupon the operating magnet such as AB1 and relay AF1 release in turn. If the switching centre subscriber fails to hang up, the release of BF1 closes timed alarm circuit AL broken when BF3 releases. Permanent loop. A timing device in the register controller releases switch BK so that BF1 closes the alarm circuit AL. Second system. Outgoing call from the switching centre, Figs. 10 to 12. Each of the two hundred subscribers of the switching centre is connected to a contact set in each primary crossbar switch AKA, there being a pair of such contact sets at each crossing point corresponding to one of the selecting magnets AS1 ...AS10 and one of the ten operating magnets AB1. Two additional selecting magnets ASH, AS12 choose that set of the selected pair which is to be connected through to one of sixty links ao ... fo corresponding to the operating bars of the primary switches AKA. By means of three secondary crossbar switches AKB similar to the primary switches, ten junctions a, b, c, associated with an operating bar in each secondary switch AKB can be connected to any of the links ao ... to. The number of the caller A1 is transferred bv the units relays AR1 ... AR10 and the tens relays AR11 ... AR30 over the control wires s5 ... s13 to the register relays BR2 ... BR9 at the exchange, Figs. 4 ... 7, 13, relay BR14 being operated or not to indicate the hundreds. digit. Relays BR11, BR12, BR10 operate in turn. In accordance with the operated register relays, in this case BR5, BR9, BR14, relays AR41, AR45 and AR38, AR39, respectively, are operated. The operations of BR12 completes test circuits including front contacts 'of the operated tens relay AR11 for free routes each including a junction a, b, c and one of the six links ao ... fo serving the caller's line. Relays BH1 associated with these free routes complete test circuits for free links a1 ... #1 to free register controllers REG 1. Supposing REG1 is connected as described above to the junction, a, b, c, relay BF1 releases BH1. Selecting magnet BS1 brings up AH3 followed by AR37, which by shunting its high resistance winding allows selecting relay AR31 associated by AR11 with the link ao ... #o to operate and disconnect the other select