Patent GB-334845-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/60
Filed: 1929-06-08
Abstract: 334,845. Automatic Telephone Manufacturing Co., Ltd., Beale, C. E., and Deyes, H. S. June 8, 1929. Semi-automatic exchange systems; party-line systemes; phantom-circuit systems; metering.-In a network of small exchanges wherein calls are set up by an operator at a central exchange, a calling party informs the operator of his requirements over a circuit (order circuit) which is different from that normally used for conversation in calls to or through the central exchange. In one system, the order circuit comprises an earthed phantom circuit superposed on a single two-wire conversational junction, while in a second system, it comprises a separate two-line junction. The order circuit may be used for subscribers' conversations if the conversational junction is busy. In the first system, a finder-connector link FS, CS, Fig. 1, preselected by allotter DA is taken into use on initiation of a call, and is connected by a hunting switch LS to trunk 25, 26 of the phantom circuit, shown at the top of Fig. 2, superposed on the junction 102, 103. The operator is signalled over the upper leg of the junction, plugs into jack J, converses over the phantom circuit, and sets CS by impulses over the same leg. If the call is for a party at or reached through the central exchange, the switch CS is set on the trunk 112, 113 leading to the physical junction circuit 102, 103 and the call is completed over jack J1. Calls incoming to a local exchange are set up by the operator over jack J1, junction 102, 103 and switch JS, and if the wanted party is busy, the operator withdraws from J1, plugs into J and redials the number. Since LS in Fig. 1 has not been taken into use, the digits are repeated' to toll connector TS, Fig. 4, which makes connection with the busy line. The wanted party replaces his receiver and the operator changes back to jack J1 and again dials the number. The switches CS, JS, TS are operated, in response to the first digit, under the control of a relay marking set which does not effectively respond to digit 1, and, as regards the second digit, by direct impulses. Two small exchanges may be connected in tandem over one or more one-way or two-way junctions. The second system in which Fig. 5 replaces Fig. 2 operates in a similar manner, the junction 122, 123 being used for control, and junction 124, 125 for inter - exchange conversations. Modified line circuits are described for magneto exchanges (Fig. 6) and for two-partyline metering (Fig. 7). The operator's cord circuit, Fig. 3, operates differently according to the kind of connection being set up; and arrangements for signalling and dealing with faults are described. Call to operator. Line relay L grounds the start lead 10 and operates S over the distributor DA to complete a series circuit for magnet FDM and relay K which, however, is short circuited by ground from non-calling or busy lines on wiper 7. The finder FS hunts for the terminal from which ground has been removed at l1, and K thereupon pulls up, connects the line wipers to feed-relay A and grounds wiper 7 to complete a series circuit for L (lower) and CO which opens the original circuit of L and completes the circuit of A. Relay K also completes the circuit of magnet DDM which steps the distributor DA to the next idle link circuit. If all the link circuits are busy, the last terminal in the bank of wiper 12 loses ground and prevents the distributor hunting continuously. Relay S falls back but K remains held over a1, k5. Relay CS energizes and completes a circuit for magnet LDM which steps switch LS in search for the seized link circuit indicated by absence of ground in the bank of wiper 23. When the link is found, CK pulls up as it is no longer shortcircuited, connects the link to trunk 25, 26 of the operator's control circuit, and disconnects it from leads 27, 28 to the toll-offering switch, Fig. 4. Relay CK also grounds wiper 23 to operate CH which starts the tone and interrupter equipment by grounding lead 13, tone being connected over cs3, ck3 to the calling party. Resistance 101, Fig. 2, is short-circuited at ck7 so that IC, Fig. 2, pulls up in series with DA, DB, Fig. 1, which remain inert, and completes a circuit for LX and LL in series over the upper wire 102 of the junction. Calling lamp CL glows, and LX operates armature lx1, Fig. 1, for a purpose to be described later. When the operator plugs into jack J, AS, AX, Fig. 3, energize in series with S, Fig. 2, and B. Fig. 3, pulls up to connect feedrelay AA and retard AB, LL falls back to extinguish the calling lamp, and LP energizes to connect battery over retard LR to junction wire 102 wire 31 and connects junction wire 102 to relay so that LX falls back and, as HK is slow-torelease, operates DS which locks to ground on LY which operates CB, CA, Fig. 1, and complete a dialling circuit to be described later. Relay CA releases CS which removes tone to indicate to the calling party that the operator has responded, CK remaining held over ca2. Call to subscribers on the same exchange. The operator throws ringing and dialling key K1 which connects up the dial switch 200 and releases AA. Relay LP responds to the first digits (2, 3 or 4) and repeats the impulses over junction wire 102 to LY, which further repeats them over wiper 24 of switch LS to a counting chain AD-CD, relays C, TD being operated over branch circuits during the train. Relay TD disconnects the conductors 17, 18 from the speaking path during dialling, and relay C operates CR to prepare a circuit for magnet CDM. Assuming the first digit to be 3, relay CD of the counting chain is operated, BD and AD released, CDM steps first over cdb, cr2 and subsequently over cd5, cd6, relay CR being maintained in a parallel circuit during stepping. When the switch comes to rest on the terminal connected to a contact of AD, CR falls back and the second digit is repeated over wiper 24, cr3, c1, g6 to magnet CDM, relay E being operated during the train to shunt g6 in case G operates when test wiper 43 passes over busy contacts. Relay E also operates ER which re-operates S and connects G to the test wiper. Relays TD, E, ER fall back at the end of the train. Busy signal and release. If the wanted line is busy, wiper 43 encounters ground, G pulls up during the relapse of ER, and locks when this relay has released. Relay G connects up the busy tone leads 15, 16, releases S, completes a further holding circuit for CH, and opens the impulse circuit. The calling party replaces his receiver and releases A and therefore K which releases CH, G, and CD. Switch CS homes. The operator is not concerned as to whether the line is busy or idle and will release the remaining equipment as described later. Ringing; completion of connection; metering. Relay G does not energize if the wanted line is idle, but, when ER has released, H energizes in series with L (lower) and CO of the wanted line, locks up, and at h3, h4 connects up ringing current from lead 14 over relay F. The calling party receives a ring-back signal. Relay H also releases S, completes a further holding circuit for CH, and releases the counting relays. The ringing trip relay F operates and locks when the called party replies, disconnects the motor start lead 13, and completes the speaking path. Relays DA, DB energize over the called loop and the circuit of meter M is completed. Normal release. This is dependent on the calling party and takes place as described in a previous paragraph. Release of equipment in setting path. As soon as the operator has dialled the wanted number, she restores K1 and withdraws. Relays S, LP, Fig. 2, release followed by LY and CB, CA, CK, Fig. 1, the wiper of LS being therefore disconnected so that LS is available for the next call. Call involving junction 102, 103 for conversational purposes. If the calling party requires a subscriber at or beyond the central exchange, the operator proceeds as before but dials a number (42) to set switch CS on terminals of the junction. The first digit results in the operation of relays AD, CD of the counting chain, so that switch CS advances to the first contact of the third group, and the second digit sets the switch on terminals of trunk 112, 113. Relay H operates over conductor 111 in series with RT (upper), Fig. 2, which locks over rt1, trips the ringing over rt2, and operates HJ which locks to 111, connects DA, DB in a loop across the speaking conductors, and completes the speaking path from 112, 113 to the junction. Relay HJ also connects battery over retard AA and balancing network to junction wire 103. When F, Fig. 2, trips the ringing, a circuit for DA, DB, Fig. 1, is completed over the aforesaid loop, but these relays do not operate and metering does not take place. Relay RT, Fig. 2, falls back. The connection of AA to 103 operates L in the central exchange, and LX pulls up to light lamps CLI and connect high resistance relay 15 to the sleeve of jack J1. The operator withdraws from jack J and plugs into J1 and proceeds in the usual manner to extend the call to a subscriber in the central exchange or over a junction to another exchange. Relay IS operates over the sleeve and connects LD to junction wire 103 in place of L so that L, LX fall back and CLI is extinguished. In the present case relays AS, AX in the cord circuit remain inert, but IA pulls up in series with LA, LB, Fig. 2, as LD does not operate at present. Relay OB, Fig. 2, is also operated. When the connection is completed, CA, Fig. 3, energizes over the called loop. Release. When the called party replaces his receiver, CA falls back, and, as CS is operated, lamp SL2 glows. When the calling party replaces his receiver, the apparatus at the local exchange restores as previously described, and the removal of ground from conductor 111 releases HJ, Fig. 2, which completes a circuit for relay A over junction wire 103 in series with LD which releases LA, Fig. 2, and IA, Fig. 3.