NL6804263A - - Google Patents

Abstract

1,179,873. Telegraphy. PLESSEY CO. Ltd. 22 March, 1968 [28 March, 1967], No. 14075/67. Heading H4P. In apparatus as described in Specification 1,024,662 comprising a local and a remote transmitter/receiver terminal, in which telegraphic information is read from a tape and transmitted to produce a corresponding remote tape record; an error-correcting system is utilized in which the exclusive supervisory channel is eliminated and data is transmitted simultaneously and contemporaneously in both forward and reverse channel directions; an error correction cycle being provided in one forward channel by initiating an error correction cycle in the other reverse channel as a supervisory signal requesting retransmission. The receiver of each channel includes means for detecting error in data received over one channel and for responding thereto by inhibition of data readout and initiation of error signal transmission from its associated transmitter over the other channel thus initiating the inhibition of data read-out at both terminals for a predetermined period for completion of an error correction cycle. At each terminal the transmitter includes a tape reader for the transmitted data and the receiver includes a tape writer for the received data, the error detection means operating to inhibit for a period of 2N data characters the tape writer of the terminal at which error is detected, for backstepping the tape reader for N characters, and for transmitting an error signal to the other terminal; the tape writer and tape reader at such other terminal being similarly inhibited and backstepped respectively. Subsequently to each backstep, the tape reader of each terminal is operated forwardly to read an appropriate character when the tape writer becomes uninhibited, so as to produce a clean copy at each terminal. Supervisory signals immediately following the error signals may be transmitted during an error correction cycle to indicate that the writer at the transmitting terminal has run out of tape. Instructions from a transmitter to a remote receiver may be sent by initiating an error cycle and interleaving control codes, and the system output is applicable to magnetic tape, on line computer, or direct printout; while input may be derived from a magnetic tape reader, on line computer, keyboard or card reader.