Patent GB-755407-A (GB)
Title: Rural satellite telephone exchange
Inventor: ORMROD DOUGLAS HENRY
IPC: H04Q3/00
Filed: 1954-12-03
Abstract: 755,407. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Dec. 3, 1954, No. 35048/54. Class 40 (4). A satellite switching centre is connected by a junction to a main exchange at which each satellite substation has an individual appearance, number, and meter, all these appearances being busied when the receiver at any satellite substation is lifted; at the main exchange a counter counts the digits dialled on a call from a satellite substation and on completion of dialling momentarily removes the busy condition from the above-mentioned appearances to permit the completion of a reverting call; on calls incoming to the satellite this counter identifies the called individual appearance and controls the selection of the wanted substation at the satellite. In the drawings, the satellite is shown in Figs. 2, 3 and 4, and the main exchange in Figs. 5, 6 and 7. Call from satellite substation C. Relay LC operates in the completed loop and brings up a common start relay ST which completes a loop on the junction and starts the operation of a pulse-generating relay PU. The first pulse brings up relay IPR, followed at the end of the pulse by IP, so that subsequent pulses are sent over the junction to step a counting chain SX-SD at the main exchange and also simultaneously step a counting chain TX-TD at the satellite. Since substation C is calling, so that relay LC is energized, the operation of counting relay TC at the end of the third pulse brings up relay K which stops the pulsing from PU and releases TB while holding TC energized. Relays TC and K effect the connection of the calling substation C to the junction, relay R operating in the loop. The slow relapse of relay LC allows relays ST and IP to fall back, K now being held by R instead of by ST. Relay BT, by self-interruption, provides busy tone to any further satellite subscriber who lifts his receiver. Meanwhile, at the main exchange, relay MP has operated in the junction loop, bringing up relay STP followed by SX and JB to busy the final selector multiple leads. Relay MP responds to loop-break pulses received from the satellite and steps the counting chain SX-SD. The first relapse of MP energizes relay MS which holds during the reception of pulses. In the present example the pulses cease at the third pulse with counting relay SC operated. This prepares a circuit for relay CM, which operates on the relapse of MS and releases SC, freeing the counting chain SX-SD. The operation of CM seizes the allocated line circuit by earthing the negative wire and also connects up the meter associated with the (calling) substation C. When the exchange equipment is ready to receive dial impulses, earth on the positive wire energizes relay SS to bring up relay HP which releases SS and completes the forward loop. Dial impulses are repeated forward by relay MP and the call proceeds in normal fashion. Call incoming to satellite substation B. When the final selector at the main exchange comes to rest on the position corresponding to the wanted substation B, earth is placed on the associated P-wire to energize relay CBP. This brings up relays JB and ICP, connecting busy earth to the P-wires of the other satellite substations and positive battery as a calling signal to the positive leg of the junction. Relay ISP operates slowly and starts the operation of pulse-generating relay PUP. The pulses are sent over the positive leg of the junction and also step the counting chain SX-SD. Since substation B is to be called, so that relay CBP is energized, the operation of counting relay SB at the end of the second pulse brings up relay SW which stops the pulsing from PUP and connects ringing current to the negative leg of the junction. Meanwhile, at the satellite, the reception of the calling signal has caused the operation of relays IC and IS, and IC responds to the pulses received from the main exchange. The first release of IC brings up relays IP and IPR, and subsequent operations and relapses of IC cause the stepping of a counting chain CA-CD. In the present example the pulses end at the second pulse with counting relay CB operated. Relays IP and IPR fall back, relay H being energized to hold CB operated. The wanted substation B is connected to the junction by the operation of CB and ringing current is received over the negative leg as described above. When the called subscriber answers, relays R (at the satellite) and F (at the main exchange) operate and the connection is completed. Relays IC and IS at the satellite fall back, but H (and hence CB) is held operated by R. Reverting call from substation C to substation B. The call proceeds initially like a normal outgoing call as described above. Dial impulses are repeated forward by relay MP, and the slow-releasing relay MS operates and releases once for each digit, stepping the counting chain SX-SD accordingly. It is assumed that a five-digit numbering scheme is employed. Relay SD is energized at the end of the fourth digit and SX at the beginning of the fifth, so that relay JB is released and removes the engaged condition from the final selector multiple. This enables relay CBP to operate at the end of the fifth digit when the final selector comes to rest on the position corresponding to the wanted substation B. Relay ICP operates, bringing up relay ISP and releasing the counting chain SX-SD, so that relay JB is re-energized and restores the busy earths on the final selector multiple. At the satellite, the calling signal is received and operates relays IC and IS as in a normal incoming call. Relay K being already operated, relay RV pulls up after IS and disconnects the calling substation from the junction, relay R, however being held operated. The wanted substation B is selected and rung as in a normal incoming call and the calling subscriber receives some of the ringing current as ringing tone through a capacitor C. When the called subscriber answers, relay F operates at the main exchange, the ringing is tripped and the call is metered. Since relays HP and SW are already operated, F brings up relay RVP, which releases the switches used in setting up the call and connects relay MP across the junction. At the satellite relay IC falls back, followed by IS and RV, completing the talking connection since both substations are now connected to the junction, over which talking battery is supplied from the main exchange through the windings of relay MP. The counting chain at the main exchange may be modified if the numbering scheme employs more or less than five digits.