GB884295A - Improvements relating to code communication systems - Google Patents

Abstract

884,295. Electric selective signalling systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Sept. 15, 1958 [Sept. 27, 1957], No. 30361/57. Drawings to Specification. Class 40 (1). In a communication system for transmitting data from a plurality of field stations to a central station each field station has associated with it a particular number and is so arranged that when electric signals representative of this number are transmitted by the central station to all the field stations they are recognized by the associated field station which then transmits its data. As described 30 field pumping stations are divided into two groups of 15 each-the field stations in each group being numbered from 1 to 15-and are selected cyclically in similarly numbered pairs, one from each group, by the central station under the control of a counter. The selection is effected by associating a particular frequency with each group and transmitting, on both frequencies, a series-mode pulse train corresponding to the number registered in the counter. A clock pulse train is also transmitted from the central station on a third frequency. The two selected field stations upon recognition of their identity number, each transmit data and independent clock pulse signals back to the central station on four more frequencies. At the central station received data is staticized and parity checked. If no error is detected the counter is advanced and the next pair of field stations is selected. If a parity error is detected the counter is not advanced and the same pair of field stations is re-selected. After three consecutive re-selections an error indication is produced at the central station and the counter is advanced to select the next pair of field stations. Communication could be via a radio link. Specification 827,008 is referred to in the Provisional Specification.