Patent GB-339345-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/58
Filed: 1929-09-05
Abstract: 339,345. Automatic Telephone Manufacturing Co., Ltd., and Gillings, C. Sept. 5, 1929. Automatic exchange metering systems.-In a zone-metering system, a group selector which responds to one digit, releases, and then responds to a second digit controls the number of metering impulses in accordance with one or the other or both digits. The selector may be a satellite discriminator which determines according to the first two digits dialled whether the call is to be completed over the main exchange or locally over the selector wipers. The invention is described with reference to the network shown in Fig. 7 comprising a main exchange ME with a satellite SE and sub-satellite SSE, a nearby exchange NE having direct junctions from the satellite SE, an adjacent exchange AE with its satellite, SAE, and a distant exchange DE. Certain features illusÀ trated in this network form the subject-matter of a divided Specification 339,600. Calls originated in sub-satellite SSE; call to main exchange (zone 3). A calling subscriber is connected over a finder to a repeater R, Fig. 1, at which relays RA, RAB, RB operate and extend the connection over a junction 6, 7 to a discrimmator SD, Fig. 3, at the satellite SE. Relays A, AB, B energize complete a circuit over con. ductors 9. 10 for relay SA, Fig. 4, which energizes unless all the outgoing main-exchange junctions 32, 31 and the hank of the hunting switch OLS are busy. Relay SA causes the switch to hunt in known manner and when an idle junction is found relay SB operates and energizes relay CH which marks the junction busy and closes a point in the chain circuit of relay ATB. Dialling tone is sent back from the main exchange and the impulses of the first digit 6 are repeated by relay A over the junction 32, 31 and to the vertical magnet VM of switch SD. At the end of the digit relay G causes the rotary magnet RM to take one step and since wiper DW (engaging with the bank DB) does not find ground a circuit is completed over magnet ZM, and contacts N2, N1 for relay E which operates to prevent further rotation and to open the vertical magnet circuit. Succeeding digits are repeated to the main exchange and when the called subscriber replies relays F, K operate reversing the current over junction 6, 7 whereby relay RD operates and energizes RDR which locks up. At the end of conversation when the calling - subscriber hangs up, relays RA, RAB fall back causing the release of relays A, AB at the satellite SD, so that at the next connection of ground to the pick-up lead 29 relay MS operates and connects wiper VW to junction conductor 7. Three impulses from lead 26, Fig. 8, are thus transmitted over conductor 7 to relay RMR which repeats them to the calling subscriber's meter over lead M. At the end of the cycle a ground connection to lead 30 energizes relay MZ which releases relays MS, K and connects battery over junction conductor 6 to operate relay RMZ. Relay RDR is thereby unlocked and the repeater R returns to normal. At the switch SD, the release of relay K disconnects relay B whereupon magnet ZM operates and restores the switch to normal. Call to adjacent exchange AE or its satellite SAE (zone 4). The first digit 8 sets switch SD as in the preceding paragraph but on the first rotary step magnet ZM operates over contact N2, wiper DW, and bank DB restoring the switch to normal. As soon as contacts N2 open relay D operates in series with magnet ZM and locks. The second digit 5 is repeated by relay A to magnet VM as well as over the junction 32, 31 and at the end of the digit relay E operates over wiper DW and lead 20 and prevents further operation of the switch SD. Metering takes place as in the preceding paragraph. four metering impulses being sent from lead 27 owing to the engagement of wiper VW with its fifth contact and to the operation of relay D. Call to distant exchange DE (zone 5). Operation in response to the first two digits 80 is similar to that in the preceding paragraph, and five metering impulses are transmitted on release over the tenth contact of bank VB. Call to satellite SE or sub-satellite SSE (zone 1). In response to the first digit 9 the switch SD operates and then releases itself, operating relay D as for a first digit 8. In response to the second digit 6 the switch is raised to its 6th level and hunting takes place in the usual manner under the control of relay G. If all local second selectors are busy contacts S operate releasing the main-exchange junction and connecting up busy tone. If, however, an idle outlet is found relay H operates in series with relay G, disconnecting relay A and thus releasing junction 32, 31. Relays AB, B release but relays D, H remain held over ground fed back to wiper 17. The connection is completed over a final selector at the satellite or at the sub-satellite and when the called subscriber replies, in addition to the reversal of current over wipers 15, 16, a booster impulse is transmitted over wiper 17 to operate relay HD which energizes relays K, B. When the calling subscriber hangs up the removal of ground from wiper 17 releases relay HD thus connecting relay MS to the pickup wire 29. Metering takes place as before, a single impulse being transmitted over the sixth contact of bank VB. Call to nearby exchange NE (zone 2). The. operation is similar to that in the preceding paragraph, the switch SD after releasing in response to the first digit 9 being further set by the second digit 1 to the first level which gives access to direct junctions to the exchange NE. During release two metering impulses are transmitted over the first contact of bank VB. Calls originated in satellite SE. These are set up in a similar manner under the control of a discriminating selector SD<1>, Fig. 7, which is substantially identical with the selector SD, Fig. 3, with the exception that metering takes place when the called subscriber replied. For this purpose relays K, AB are eliminated and the circuit of relay MS is completed by relay F for calls to or through the main exchange and by relay HD for calls over the wipers 15 - - 17. Calls originated in exchanges AE or DE. For first digits 6 or 9 the first selector, Fig. 14, operates in known manner and when the called subscriber replies relay PR energizes in the a-wire and connects up relay MS to initiate metering as before, the number of metering impulses being determined in accordance with the first digit by wiper VW. For a first digit 8, post-springs NP operate closing a circuit for the release, of magnet Z. When off-normal springs N3 open, relay F operates over a contact of magnet Z, disconnecting the circuit for the release magnet and closing a short-circuit across springs' NP2 so that hunting will occur in the usual manner after the receipt of the next digit. Metering in this case is dependent upon the second digit. Calls originated in satellite SAE. The first selectors are similar to Fig. 14 but metering takes place on release in a manner similar to that for calls originated in sub-satellite SSE. Calls originated in main exchange ME. The first selectors are similar to Fig. 14 but with relay F, normal contacts N3, and post-springs NP eliminated so that metering is always determined by the first digit. Modified first selector absorbing the second digit, Fig. 12. The first digit operates the vertical magnet VM and on the relapse of relay C, relay DA operates disconnecting the vertical magnet. The second digit is repeated through relay C and a resistance without effect on the wipers, relay C causing the operation of relay DB so that at the end of the digit a circuit is completed for the rotary magnet RM and hunting takes place as usual. Metering takes place as in Fig. 12 and is determined by the value of the first digit.