Patent GB-748072-A (GB)
Title: Electrical communication system
IPC: H04Q11/04
Filed: 1951-01-10
Abstract: 748,072. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Jan. 10, 1951 [March 18, 1950], No. 708/51. Class 40 (4). [Also in Group XL (c)] Groups of substations are each connected to a party line, and each substation is allotted a time position in a recurring cycle of time positions spaced between recurring reference timepositions characteristic of the party line. Each party line which may be a radio link is connected to an aligning circuit having outlets equal in number to and individual to the time positions and pulses incoming to the aligning circuit are routed to the corresponding outlets and leave the aligning circuit in the reference time position of the party line. Thus a group of one hundred subscribers are allotted time channels SO ... S99, Fig. 1, equally spaced between the reference pulses R. When a subscriber in exchange A calls, his channel pulse appears on a party line 102A, Fig. 4, and is passed through an aligning circuit 110A over an outlet corresponding to the caller and a mechanical or electronic finder to a switch 111A which includes delay and aligning circuits. The switch 111A delays the channel pulses by an amount determined by signals transmitted by the caller and its aligning circuit sends pulses in a time channel characteristic of the switch 111A over an outlet corresponding to the delay and leading to a multi-channel junction 113A to the wanted exchange B. The junction channels are separated by an incoming aligning network 114B. In a similar manner the connection is extended over a switch 116B and an aligning network 117B which sends pulses in the reference time position of the wanted party-line to the switch 118B, which is set by the caller to delay the pulses to the time position of the called party. Speech is transmitted by modulating the channel pulses. Party-line, Fig. 3. The subscribers' substations S0 . . . S99 on a party-line are connected in parallel between a series of delay networks L0 ... L99 and go and return-pairs 102, 103 respectively. When a subscriber calls the reference pulses R of his party-line passing through the delay networks trigger a pulse generator at his substation, so that his channel pulses, say S99, at the proper spacing from the reference pulses R are fed to the aligning circuit connected to the go-pair 102. Aligning circuit, Fig. 7. The pulses S of all the calling subscribers and the reference pulses R are passed through a delay line 122 to which are connected 100 outlets L0 . . . L99 each individual to a subscriber. The reference pulses R being of larger amplitude than the channel pulses S0 ... S99 are passed by a biased rectifier 123R and simultaneously prime coincidence circuits consisting of rectifiers 123 or pentodes and controlling the outlets at a time when the calling pulses are opposite the respective outlets. Thus, calling pulses are simultaneously transmitted on separate outlets in the time position of the reference pulse R of the party line. Switch, Fig. 8. The outlets of an aligning circuit are connected by finders 140 to switches. The caller sets the switch by transmitting one or two of frequencies 100, 122, 148, 180 cycles which are detected by band-pass filters F1 ... F4. One or two of relays 145f1 . . . 145f4 lock up and connect in their associated delay networks 146f 1 . . . 146f4 having delays 1, 2, 4 and 7 channel spacings respectively. The delayed pulses are fed to an aligning circuit 228 which switches the pulses to the outlet 230 corresponding to the delay. The gating pulses are obtained from the incoming pulses which are passed through a delay network 232. Corresponding outlets of all the switches are commoned to outgoing junctions or trunks, individual delay lines being inserted where necessary to bring the pulses from separate outlets into separate channels. A similar switch having 100 outlets and two sets of delay lines set by two separate signals from the caller is described. Specification 651,781 is referred to.