Patent GB-357232-A (GB)
Title: Circuit arrangements for automatic or semi-automatic telephone exchange systems
IPC: H04M15/10
Filed: 1930-06-19
Abstract: 357,232. Exchange systems. STANDARD TELEPHONES & CABLES, Ltd., Columbia House, Aldwych, London.-(Bell Telephone Manufacturing Co., Soc. Anon. ; 18, Rue Boudewyns. Antwerp, Belgium.) June 19, 1930, No. 18704. [Class 40 (iv).] In a zone metering arrangement, local trunks are each provided with a timing device and outgoing junction circuits are provided with rating devices, and on reply of the called party, the timing device sends a signal to the first outgoing junction circuit of the chain which sends back metering impulses and then sends a forward signal to the next outgoing junction circuit which operates in a similar manner. These operations are repeated at intervals during the conversation. The metering impulses may pass direct to subscriber's meter during conversation, but, as described, they are stored on a switch associated with the timing device and transmitted to the meter at the end of the conversation. The arrangement is applicable to full automatic and manual systems but is described in connection with automatic metering in a toll system in which a calling party is connected over group selectors, Fig. 2, to a recording trunk RTC, Figs. 1 and 3, which an operator (referred to subsequently as the A-operator) connects by cord circuit TCC, Fig. 1, to an outgoing junction circuit OJRC. The operator at the incoming exchange (B-operator) connects the incoming junction circuit IJRC to an outgoing circuit to another exchange where a further operator (C-operator) connects the incoming circuit to a local trunk. The incoming and outgoing junction circuits are symmetrical and adapted for two-way working. Direct or alternating current may be used for metering and supervisory signals, and when repeaters are used, arrangements are provided for byepassing the signals. Setting up of connection. When the A-operator has taken the recording trunk and an idle outgoing junction circuit, Fig. 4, battery over the sleeve of the calling plug operates OC, OSR which lock up in series and energize OCX so that interrupter R1 is connected over the sleeve circuit to relay FL which flashes SL2. Relay OCX also connects battery to the outgoing a-wire to operate IA1 followed by IT, IBS at the incoming end, Fig. 3. The junction busy signal operates over BS. The B-operator on taking the call and plugging an outgoing junction circuit similar to Fig. 4 operates OC, OSR, OCX in this circuit and similar operations follow at exchange C when the operator completes the connection. Reply signals. On reply of the wanted party, battery over high resistance is connected over the b-wire of the C-cord circuit and operates IU at exchange C followed by IG and IA which energizes a differential winding on IT to release this relay. Relay IU repeats the battery signal over the b-wire of the B-C junction to operate OB1, OB (exchange B) which by disconnecting battery from the outgoing a-wire releases IA1, IA at exchange C. At exchange B, relay OB1 connects battery over OR, which remains inert, to the b-wire and similar, operations in exchanges A, B follow. At the outgoing circuit at exchange A, the battery connected up by OB1 extends over the b-wire of the cord circuit to relay O, Fig. 3, which is held throughout the connection both from the outgoing circuit at A and also by relay S which is energized by the supervisory relay Spr in the trunk circuit RTC operated in known manner. Metering. Relay O starts the timing switch TS which on reaching its first contact energizes CT which connects low resistance relay IS to the b-wire so that OR in the outgoing circuit operates. Relay IS operates LM. Relay OR completes a circuit for slow interrupter ST1 over the left-hand winding of OH, which prepares a circuit for OI and connects an impulsing interrupter M1 to the b-wire. When ground is disconnected at ST1, relay OI operates over its left-hand winding in series with the left-hand winding of OH and locks over both windings to OH (2), but when ST1 reconnects ground OH falls back, and OI remains energized over its right-hand winding until ST1 again disconnects ground. OH is prevented from reenergizing by OM which locks to OR (1) after the relapse of OI. Interrupter M1 is therefore connected up during one revolution of ST1, and IS, in response, steps switch SM1. Interrupters M1 may be individual to junction groups requiring the same charge and ST1 common to all junctions, or, M1 may be common to all junctions, the different groups being provided with individual interrupters ST1. Relay OM connects battery to the outgoing a-wire to operate IAI at exchange B and IA operates to short-circuit the high resistance winding of IU so that OR in outgoing circuit at exchange B pulls up and initiates the sending of metering impulses from exchange B. These impulses are repeated from B to A by IU which is intermittently short-circuited by M1 and opens the battery connection to the b-wire of junction AB. The switch SM1 has now been stepped over contacts equal to the sum of the impulses representing the rates of the two junctions and the timing switch TS moves off its first contact thus releasing CT, Fig. 3, and relays OR, OM in the outgoing circuits. As switch TS reaches succeeding contacts which are spaced to reduce the tariff for calls of long duration, a signal is sent forward to initiate the transmission of similar further sets of metering impulses. If the duration of conversation reaches a predetermined limit, BR, Fig. 3, pulls up and SL1 is flashed to signal the operator. When the calling party replaces his receiver and the A- operator withdraws, relays S, O, Fig. 3, fall back and interrupter S1 is connected to relay C which locks up and connects S1 over wiper c of SM1 to relay SO which repeats impulses to the magnet of the outstepping switch SM2 and also to metering relay Mtr, Fig. 2, over the c-wire. When SM2 reaches the same position as SM1, SM opens the impulsing circuit, SM1, SM2 go home in turn, and C falls back. Relay Mtr repeats the metering impulses to relay Gtr, subscriber's meter being operated by further repetition by RMR. Supervisory lamp signals. As previously described, the outgoing supervisory lamps SL2 are flashed by interrupters R1 as each operator takes a junction into use. On reply of the called party, the relays OB in the outgoing circuits disconnect the interrupters R1. When the calling party replaces his receiver, the relapse of supervisory relay Spr short-circuits the high resistance winding of SR so that lamp SL1 of the A-operator lights. When the called party replaces, lamp SL2 of the C-operator lights and the removal of the previously mentioned high resistance battery on the b-lead releases IU which removes battery from the b-wire of the B-C junction to release OB, OBI at exchange B leaving OCX, OC, OF operated. Relay OB connects battery back over the B-C junction a-wire to operate IAI, IBS at C, while ground over the left-hand winding of OF lights lamp SL2 of the B-operator's circuit. The relapse of OBI at B similarly results in lighting lamp SL2 at A and the operation of IA1, IBS at B. The A-operator, seeing both lamps lit, withdraws so that OC, OCX, OF in her outgoing circuit fall back and IA1, IBS at B release and operate IC in series with SL1. The B- operator withdraws and SL1 at C is similarly lit up to give the C-operator the clearing signal. Modified circuits, Fig. 7, for A.C. signalling and for use with repeaters. This figure may be read as an incoming or outgoing circuit and in the following description I or O will be prefixed to the relay designations shown, according to direction of use. The operation of this circuit, except for matters described below, is the same as that described for Figs. 4 and 5. When an outgoing circuit is seized (from left-hand end in this case) OC, OCX pull up as before and connect 50-cycle current over contacts of OB and filter circuits to the outgoing junction to energize IA1 at the incoming end. When IU operates on reply of the called party 20-cycle current is connected back over the B-C junction to operate OBI, OB at exchange B. OB disconnects the outgoing 50-cycle supply. After the first set of metering impulses have been sent back from the outgoing circuit on exchange A, OM operates as before and connects 50-cycle current to the A-B junction to operate IA1 at B. The metering impulses from the outgoing circuit at B are repeated at the incoming circuit at B by intermittent release of IU as before which in this case intermittently disconnects the 20-cycle supply which intermittently operates OB1 at A. Other supervisory A.C. signals are controlled by IU, OB in a similar manner. It will have been noted that battery is connected to the outgoing a-wire, Fig. 4, until the answering signal is received, and that the same connection is used later for initiating the transmission of metering impulses. The answering signal also prepares incoming junction circuits f)r the reception of the said metering signal. There is a time lag in the latter operation to prevent the original battery connection acting as a metering signal. When a repeater is used, this lag is increased by the provision of slow releasing relay IAX which is operated by IA1 when the circuit is awaiting the answering signal so that when this signal is received and IA is operated, the release of IT is delayed. Two-way repeaters. These are byepassed by circuits shown in Figs. 6 and 8 for D.C. and A.C. signalling respectively. In Fig. 6, relays AE, AW repeat the a-wire signals and BE, BW the b-wire signals. In Fig. 8, 20- or 50-cycle current in one direction passes over one or other of two filters and operates AE or BE to connect up the correct outgoing signal, while AW, BW operate similarly in the opposite direction.