Patent GB-651835-A (GB)
Title: Improvements in or relating to automatic telephone exchanges
IPC: H04M15/00
Filed: 1947-04-08
Abstract: 651,835. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. April 8, 1947, No. 9337. Convention date, April 8, 1946. [Class 40 (iv)] In a multi-metering arrangement, a common rate determining device ZZ, Fig. 1, is set by the register REG in accordance with the routing digits and is subsequently associated temporarily with the outgoing junction equipment REP, which controls duration metering; to deliver the metering rate thereto. When the routing digits have been stored on a 4 X 10 cross-bar switch B1 . . . B4 in the register, Fig. 2, a circuit is completed for relay RR2 in series with a discharge tube GL, the connection shown as a broken line and a high resistance r1 in ZZ, Fig. 3. Relay RR2 closes a circuit over wire d and the group selector GV1 for relay UR7 to connect the junction equipment REP, Fig. 4, to the device ZZ. If more than one device ZZ is provided, each is allotted to particular directions of traffic and the circuit of RR2 includes contacts of bar B<SP>1</SP>. If two registers connect simultaneously to the same ZZ, relay R1 pulls up to release the relays RR2 and therefore both registers. Four-digit routing number. A selecting magnet, e.g. STM1, of a cross-bar switch in the device ZZ is operated via the bar B1, whereupon an operating magnet, e.g. BM10, is actuated over the circuit from contact 31 of STM1 and the bar B2. The rate selection is completed by the operation of one of the relays RIO ... R19, e.g. R11, over the closed contact set of the bar B4, which completes a circuit over the closed contact set, e.g. 1, of the bar B3, contact set C1 and wire 4 of the rate signalling group 1 . . . 8, for a combination, in this case UR8, of the group of rate-determining relays UR8 ... UR11. Three-digit routing number. Supposing the first two digits registered on the bars B1, B2 are such as to effect the operation of, e.g. magnets STM10, BM10, the closed contact set of the bar B3 completes a circuit over a switch contact such as B10, to one wire of the rate signalling group 1 ... 8. Two-digit routing number. Supposing the first two digits are 9, 0, magnets STM9, BM10 are actuated to complete a circuit over C9 to the rate signalling wire 5. Single-digit routing number. A first digit 2 effects actuation of magnet STM2 to complete a circuit to the rate signalling wire 5. Junction equipment and metering. When the appropriate relays of the group UR8 ... UR11 operate, relay UR7 is disconnected together with winding II of RR1. The latter operates over winding I and relay RR2 pulls up to free the device ZZ. Junction FLI is seized by battery connected to wire c and UR6 pulls up to send an A.C. call signal during the operating period of relay UR1 and then during the release of UR6 relay UR2 locks up. The register emits audio-frequency signals over the junction FL1. On completion of the connection, an answering signal temporarily operates relay UR5, which may be used to operate a high resistance relay to release the register. On reply of the called party, UR4 is connected in series with a low resistance relay and locks up to feed to relay UR12 impulses from sources I ... VIII, varying from 20 per second to one per two seconds and selected by the setting of relays UR8 . . . UR11. A ratchet-wheel S is stepped and after a certain number of impulses actuates contact 121 to send a metering impulse over wire d to the caller's meter and at the same time the releasing winding y of UR12 restores the ratchet-wheel S to its original position. Release. UR1 falls back to operate relay UR3 and UR6 follows, closing a fresh circuit for UR1 so that these relays interact and A.C. signals are emitted over FL1 repeatedly until UR5 is operated by a backward signal over FL1. A time-controlled alarm AL is operated if the backward signal is not received. On disconnection, UR5 operates to release UR3 and general release follows.