Two-way transmission of baseband digital signals

This paper investigates a novel technique for the transmission of baseband digital signals over a cable in both directions simultaneously. The arrangement relies on the use of narrow transmitted pulses which, after suitable line equalisation, yield substantially wider received signals. Directional separation is then obtained by exploiting the local difference between the transmitted and received signals. Three important areas of difference between this scheme and its one-way counterpart are identified and studied. These are directional discrimination, detection and timing extraction. It is shown that although the mutilation of the received signal by the transmitted pulse will increase the vulnerability of the two-way system to digital errors in the presence of noise, for some applications, this will be trivial compared with other methods of achieving the same total information rate. The technique has potential for application in the local telephone network and in submarine cable systems where, for good reason, only one cable pair is available.