Radio relay systems

1506710 Radio systems SIEMENS AG 8 Aug 1974 [8 Aug 1973] 14566/74 Heading H4L In a radio relay system two subscribers have respective transceivers and utilize a single frequency channel which includes means by which the information flow provided by the particular transmitting subscriber ("go" connection) is periodically interrupted for a time short compared with the transmission time to form a time slot channel for return connection of a lower transmission capacity than that provided by the channel for information flow, the time slot channel being utilized for information transmission in the return direction. In the embodiment the subscriber receiving at any time can change the direction of transmission at will. General arrangement, Fig. 1.-A communications network includes tandem central offices 1,1, 2, radio concentrators 5, 6 each containing several transceivers SE, and mobile stations A &c. Frequency schedule, Figs. 2a, 2b.-Each subscriber is accessible through five frequency channels Fig. 2a and a binary code is utilized for ringing tone to include selection of the channel being used for calling, Fig. 3 (not shown). To reduce susceptibility to interference a converter U, Fig. 2b is employed to change the frequencies of the channels used by a group of subscribers, e.g. each hour. Mobile station, Fig. 4.-A pulse delta modem 16 is followed by a unit 17 which time-compresses the modulator output and affords the time slots, and time-expands its input before demodulation. A cipher means 18 is included. The R.F. channel utilized is produced by a synthesizer 24. For calling another subscriber the desired number is fed from dialling set 26 into a computer 27.