Video disc sound recording - uses TDM to separate sounds recorded on different channels and subcarrier reference signals to discriminate between sounds

摘要

A number of sound signals are recorded by pulse code modulation on a videodisc, each signal being separated from each adjacent signal by a unique subcarrier signal (Fm) recorded on a full turn of the disc. A number of sound signals are recorded on a single multiplex channel, each channel being identified by a channel signal Yn) and the channel signals being recorded in respective disc sectors between recorded synchronising signals (SY). The desired channel and subcarrier signal are selected for the required sound signal by respective selection switches. A reading head then rapidly radially scans the disc until the selected subcarrier is detected by a corresponding filter. Normal head reading then commences. A clock driven ring counter receives and is reset by the synchronising pulses and then passes the selected channel signals to a demodulator, the relevant ring counter output having been selected by the channel slection switch.