Synchronizing signal discriminator for use in channel selection apparatus of television receiver

DETAILED DESCRIPTION What we claim is: 1.
A synchronizing signal discrimination circuit for use in a channel selection apparatus having a preset function of a television receiver, comprising; (a) a timing pulse generation circuit for generating a first time interval signal having a first predetermined pulse width after a reset signal has been applied thereto and a second time interval signal having a second predetermined pulse width after the expiration of said first time interval signal, (b) an input terminal for receiving an input signal, (c) a noise detection circuit connected to said timing pulse generation circuit and said input terminal for receiving said first time interval signal from said timing pulse generation circuit and said input signal from said input terminal, said noise detection circuit being operable to produce a noise detection signal only when said first time interval signal and said input signal are simultaneously applied thereto, (d) a periodic signal detection circuit connected to said timing pulse generation circuit and said input terminal for receiving said second time interval signal from said timing pulse generation circuit and said input signal from said input terminal, said periodic signal detection circuit being operable to produce a periodic signal detection signal only when said second time interval signal and said input signal are simultaneously applied thereto, (e) a reset signal generation circuit connected to said noise detection circuit and said periodic signal detection circuit for producing a reset signal when either said noise detection signal or said periodic signal detection signal is applied thereto, said reset signal being supplied to said timing pulse generation circuit, and (f) a first output gate circuit connected to said noise detection circuit and said periodic signal detection circuit, said first output gate circuit being reset when said noise detection signal from said noise detection circuit is applied thereto and set when said periodic signal detection signal from said periodic signal detection circuit is applied thereto to produce a first output signal