Patent GB-1012133-A (GB)
Title: Improvements in or relating to translation systems
IPC: G06F3/06
Filed: 1961-12-05
Abstract: 1,012,133. Electric selective signalling systems. WESTERN ELECTRIC CO. Inc. Dec. 5, 1961 [Dec. 15, 1960], No. 43442/61. Heading G4H. General.-In a satellite tracking system, azimuth and elevation control signals are received at the tracking station together with a coded representation of the time at which the command signals are to be used, and a comparison of the coded time with signals representing the local time is made, the control signals being utilized if the coded and local times correspond, or, in the event of non-correspondence of the times, comparison between the local time and the next coded time is made and is maintained until correspondence again occurs. System details.-Blocks of data received for example over a teleprinter channel are punched on tape. A typical block of data is shown in Fig. 2 and is read in the order top to bottom. The left-hand digit of each character is a parity digit. The coded time and the control signals are represented in binary coded decimal form, and each signal or word is followed by an identifying tag which is unique to that signal. The third character of the azimuth- and elevation-rate words indicates the sign of that quantity. A complete block of data is read every two seconds and the character-representing signals from tape reader 300, Fig. 3, are applied to a parity check circuit 301 which prevents mutilated signals from being used. Each character is also examined by a tag decoder 302 which has six output leads, one of which is marked to signify that a character being read is not a tag, and the remaining five are selectively marked to identify which tag is being read. Characters which are not tags are entered in word assembly register 303. Thus when a time tag is identified by decoder 302, the associated coded time has previously been entered in register 303 for comparison at 305 with the local time; the result of this comparison being then gated out. If the times do not correspond, the tape is advanced until the next time tag is detected and a further comparison made. If the times still do not correspond, the tape is halted and a continuous comparison of the local time and the coded time in register 303 is made until correspondence occurs. When the two times are in agreement the comparison circuit gates the successive control signals from register 303 to respective translation circuits, the azimuth and elevation translators each comprising coarse and fine translators. Each translator comprises a counter which is set to the number supplied thereto by register 303, the counters being then counted down by clock pulses to give variably timed output pulses as they pass through zero. Interpolation.-During the two-second interval between blocks, each counter of a translator is cycled 1000 times, the output pulse occurring in the same position in each cycle if no interpolation occurs. If the rate sign is positive, the output pulses from the rate translator are converted to pulses whose duration represents the rate, and each of the pulses is used to inhibit clock pulses supplied to the fine translator. If the sign is negative, pulses are supplied to the fine translator at twice the normal frequency for the duration of each rate-representing pulse. In this way the effective setting of the fine translator is advanced or retarded by equal increments in each cycle. A similar principal is employed for the coarse translator. Specification 1,012,132 is referred to.