Multiple standard TV receiver - uses difference between audio and video carrier frequencies to select incoming signal standard

摘要

The multiple standard t.v. set automatically switches its standard to that of the incoming signal. The circuit (1) produces a voltage dependent on the difference between the audio and video carrier frequencies. A selective narrow band amplifier (F1, T1, F2, T2,) selects the difference frequency from the modulated intermediate audio at its input. The amplifier is gated during the line flyback by the flyback pulses in the transmitted t.v. signals and its output is detected (D) to produce the voltage which is used to select the required module for the transmitted signal standard.