System of recording and playback of digitally recorded signals,

Abstract

Four magnetic heads are provided on a rotary mount equally spaced around the circumference, so when they are rotated to scan a tape wound around the headwheel in half a turn of a helix, each oblique track on the tape corresponds to half a revolution of the headwheel. In recording, the incoming signals are subdivided in time demultiplex into segments alternately distributed first to one diametryl pair of heads on the headwheel and then to the other diametryl pair, in each case through a digital time expander that doubles the time required to transmit the signal segment, thus reducing the bit rate by half. The reverse operations are done in playback, with time-expansion before the signal segments are put together into a continuous signal channel stream at the original bit rate. If the time-expansion is by just a little less than the factor of two, and the time-compression likewise, the places on the tape where two heads of the same channel would instantaneously both be in contact with the tape are left clear of signals, and disturbances are avoided, without interfering with the continuity of the playback signal.