TV monitor

Claim 1

In a system for monitoring the reception status of a television receiver capable of detecting selected ones of a plurality of wave signals, each representing a separate video channel, said receiver including an antenna for receiving said wave signals, a horizontal retrace circuit and a kinescope circuit, monitoring apparatus comprising: first probe means connected to said horizontal retrace circuit for detecting a voltage in said horizontal retrace circuit; second probe means connected to said kinescope circuit for detecting a signal frequency in said kinescope circuit; voltage level detector means connected to said first probe means for detecting a predetermined level of the voltage on said first probe means; first logic means connected to said voltage level detector means for providing a first gate signal when said voltage level detector means detects a voltage on said first probe means less than said predetermined level and providing a second gate signal when said level detector means detects a voltage on said first probe means equal to or greater than said predetermined level; second logic means connected to said second probe means for providing a first signal representative of the signal frequency detected by said second probe means and providing a third gate signal between successive horizontal blanking periods on an active video line of said kinescope circuit; oscillator means for selectively generating one of a plurality of radio frequency signals within the bandwidth of the wave signals representative of separate video channels, antenna coupling means for selectively coupling said television receiver to said antenna and to said oscillator means; gate means connected to said first and second logic means and to said oscillator means and said antenna coupling means and responsive to said second and third gate signals for operating said oscillator means to generate a radio frequency signal within the bandwidth of a channel and for operating said antenna coupling means to couple said television receiver to said oscillator means and decouple said antenna from said television receiver, thereby impressing said radio frequency signal onto the antenna input of said television receiver between horizontal blanking periods on an active video line; compare means connected to said oscillator means and said second logic means for comparing the frequency of the signal generated by said oscillator means with said first signal representative of the signal frequency detected by said second probe means; control means connected to said compare means and to said oscillator means and responsive to a non-coincidence of signals compared by said compare means for controlling said oscillator to generate another radio frequency signal upon the next operation of said gate means; and transmitter means connected to said first logic means and to said compare means and responsive to said first gate signal for transmitting status data indicative that said television receiver is in an "off" condition, and responsive to a coincidence of signals compared by said compare means for transmitting status data indicative that said television receiver is in an "on" condition and indicative of the channel to which said television receiver is tuned.