Error Rates and Error Detection on Telegraph Circuits

This paper reviews error rates obtained in tests on the full range of telegraph facilities provided by an administration at signalling speeds not exceeding 200 bauds. The telegraph facilities tested include: an inland private circuit, automatic switched circuits, international circuits, intercontinental circuits in a submarine telephone cable, a speech plus telegraphy facility on inland telephone circuits. For transmission of data with a character error rate of better than
1/10^{6}
on cable circuits, an improvement in performance will be necessary, and as this is unlikely to be obtained economically by attention to the cable or telegraph networks; the improvement will have to be achieved by error detection and retransmission. Where a short renter-to-renter circuit is involved, it may be satisfactory to use automatic error detection and manual retransmission, but over other telegraph facilities automatic retransmission may be necessary. Tests have also been made on both unprotected radio telegraph circuits and circuits employing the Van Duuren automatic error correction (ARQ) system. An appraisal is made of the over-all performance of this system, with suggestions for improvements necessary for the transmission of data. Where a duplex telegraph circuit is available, a simple method of error detection is to feed the received signal back to the sender where it can be checked against the original.