GB1157360A - Error-Correcting Digital Transmission Systems - Google Patents

Abstract

1,157,360. Digital transmission systems. INTERNATIONAL STANDARD ELECTRIC CORP. 7 Sept., 1967 [15 Sept., 1966 (2)], No. 40944/67. Heading H4P. In a digital transmission system in which data is sent in equal length blocks of multi-bit signals, each signal being checkable for errors, and in which the blocks are sent continuously in both directions between two stations, the first signal in a block indicates the occurrence of error in the last block received. The signal indicates which signals in the received block were errored and causes repetition of those signals as the second and subsequent signals of the next block to be transmitted, unless the signals have already been corrected as described below. If the first signal of a block is errored the whole block is repeated. If no error is detected the first signal of the next transmitted block may be a data signal. If a station has no data for transmission it sends blocks of idle signals. In such condition when a signal is errored a repetition-requesting signal is immediately sent, and on reception of the latter the appropriate signal is immediately repeated. If the correction is completed prior to the end of the block in which error occurred the first signal of the next block sent from the station which detected the error does not indicate the presence of the error. On the other hand if the correction was not completed at that time the first signal does indicate error but no repetition is initiated on account of this since the errored signal will be repeated in response to the repetition-requesting signal.