Facsimile video remodulation network
Abstract
Abstract THIS DISCLOSURE DESCRIBES AN APPARATUS FOR RESTORING AND IMPROVING FACSIMILE VIDEO SIGNALS THAT HAVE BEEN DEGRADED PRIOR TO RECEPTION. THE INCOMING VIDEO SIGNAL IS DEMODULATED AND APPLIED TO A LINEAR DIFFERENTIAL AMPLIFIER CIRCUIT AND TO A CONTROL CIRCUIT CONNECTED IN PARALLEL WITH THE LINEAR DIFFERENTIAL AMPLIFIER CIRCUIT. THE CONTROL CIRCUIT CONTROLS THE RESTORING OF THE DEMODULATED SIGNAL BY LINEARLY CONTROLLING THE BLACK LEVEL OF THE VIDEO SIGNAL OR BY NONLINEARLY CONTROLLING THE DIFFERENCE BETWEEN THE BLACK AND WHITE LEVELS OF THE VIDEO SIGNAL PASSING THROUGH THE LINEAR DIFFERENTIAL AMPLIFIER. THE INVENTION ALSO INCLUDES MEANS FOR DETECTING THE FREQUENCY OR VIDEO CARRIER SIGNAL AND USING THE DETECTED SIGNAL TO CONTROL A SWITCHING NETWORK. THE SWITCHING NETWORK SWITCHES ITS OUTPUT AT THE FREQUENCY OF AND COHERENTLY WITH THE INCOMING SIGNAL. THE OUTPUT OF THE SWITCHING CIRCUIT MODULATES THE RESTORED VIDEO SIGNAL IN A MODULATOR. HENCE, THE OUTPUT FROM MODULATOR IS A RESTORED VIDEO SIGNAL HAVING A CARRIER FREQUENCY THAT IS THE SAME AS THE CARRIER FREQUENCY OF THE UNRESTORED (INCOMING) VIDEO SIGNAL.
Inventors
- 👤 Charles H Vermillion
Bibliographic Details
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