Unidirectional transmission system for packet data - uses demodulator to recover synchronisation and data bit frequency for validation and error correction circuits

摘要

Several data sources are multiplexed in a control unit for application to a modulator which also receives the video signals for transmission to a number of receivers. The TV receiver provides a video output for a demodulator. This comprises an impedance matching circuit to drive a sync. circuit and recovery circuit to recover the frequency of the data bits in the packet transmission. These allow the demodulator to recognise the starting octet for the data to ensure that succeeding data is transmitted to a logic circuit. This contains registers and control circuits to pass the received data to validation circuits. An error correction circuit provides signals for a cross coder followed by a formatter to output the data to a terminal.