Circuit arrangement for identifying television signals

Abstract

The circuitry is used, for identifying television transmitters, in a television set receiving synchronizing signals and line flyback pulses characteristic of television transmitters, particularly for television receivers including a station finder circuit. The circuitry, during the time period of the line flyback pulses, derives samples of those signals appearing above the black level of the video signal, from the demodulated input signal. The number of amplitude jumps determined during the time period of the line flyback pulses is utilized as the criterion for identification of a television transmitter. The signals appearing above the black level of the video signal are inverted and then combined, in an AND circuit, with the line flyback pulses, and the output of the AND circuit is connected to a digital counter circuit to supply the output pulses thereto as counting pulses, with the flyback pulses being supplied to the digital counter circuit as gate pulses. An inverter is connected to the output of the counter circuit and a logic '1' potential appears at the output of the inverter only in the case where a single pulse has been delivered to the counter circuit during the gate time, with a logic '0' potential appearing at the output of the inverter in all other cases. The output of the inverter is connected, through an integrating circuit, to a threshold circuit providing an output signal which indicates whether a television transmitter has been identified.