Patent GB-1250365-A (GB)
IPC: H04B7/212
Filed: 1969-09-29
Abstract: 1,250,365. Telephone systems. SIEMENS A.G. 29 Sept., 1969 [30 Sept., 1968], No. 47755/69. Heading H4K. Ground stations in a space-satellite communication system each transmit in a permanently associated burst period of the system tdm cycle, a supervisory channel in each burst giving the identity of the other ground stations with which connection is required and indicating also the identity of the tdm channels within the burst employed for such connections, the received bit stream at a station being set up by a serial-toparallel converter to comprise words relating to each channel, a group of links being provided between a ground station and an associated exchange, one such link being seized in respect of each channel set-up to the station over the satellite, each link being associated with a buffer store at the ground station. Which store receives a channel word in the time slot of the incoming channel and holds it pending demodulation on to the link. A station's transmission burst comprises an initial synchronizing code, an own station code, the supervisory channel bits, and the bits of the speech channels which may be accompanied by telegraph and data channels. As shown in Fig. 3 the received bit stream at a ground station is fed from a series-to-parallel converter SPU to a 7-bit bus LV. Exchange links A1 to An have associated buffer stores 1 to n between the input bus LV and output bus LV<SP>1</SP>. Data from the supervisory channels is utilized in control circuit VSp to operate gates S11 to S1n to steer incoming channel words to the buffers of links seized for the connections, the words being set up on capacitative stores C11 to C1n. During a station's own transmitting burst period, as relayed back from the satellite, gates S11 to S1n are all open and gates S21 to S2n are closed to transfer all the words received in one system cycle to the capacitative stores C21 to C2n. In the subsequent system cycle, while further words are accumulated on stores C11 to C1n, the words of the previous cycle are extracted by gates S31 to S3n and are demodulated on to the associated links A1 to An. Gating on to a common bus LV<SP>1</SP> allows the use of a common pcm digital to analogue conversion at DAU. When a link is seized in respect of a call incoming over the satellite the identity of the link is recorded in a store in a position which identifies the incoming call channel time in the system tdm cycle. Such storage may be on a magnetic drum the storage compartments of which are sequenced to match the system channel times and the identity of a seized link being recorded in the storage compartment corresponding to the channel of an incoming call, Fig. 3 (not shown). Such storage may, alternatively, be effected on a thin film or core coordinate store each column of which relates to the burst transmission of another ground station and the rows of which relate to the channels in each burst. With such storage of a seized link identity incoming channel words are steered to the appropriate buffer stores. A station to which a connection has been established over the satellite responds by setting up a connection in the reverse direction to the calling station to complete a four-wire link.