Line oscillator synchronizing circuit

Claim 1

A television receiver having a line deflection circuit and a line synchronizing circuit, said line synchronizing circuit comprising a controllable oscillator, a signal derived therefrom being applicable to said line deflection circuit; a pulse generator coupled to said oscillator for deriving pulse-shaped gate signals; a coincidence detector; means for applying said pulse-shaped gate signals and pulse-shaped line synchronizing signals to said coincidence detector; a first phase discriminator coupled to said coincidence detector for determining the phase difference between said line synchronizing signal and a reference signal derived from said oscillator signal; a first low-pass filter for smoothing the output voltage from said first phase discriminator, said controllable oscillator being coupled to said first low-pass filter whereby the output therefrom controls the frequency and/or phase of said controllable oscillator; a second phase discriminator for determining the interval between the center instant of a pulse of said pulse-shaped gate signal and the center instant of an edge occurring in said reference signal; a second low-pass filter for smoothing the output voltage from said second phase discriminator; and means for controlling the center instant of the edge in said reference signal using the output from said second low-pass filter; wherein said line synchronizing circuit further comprises gate means having a first input terminal for receiving the output from said pulse generator and a second input terminal for receiving an output signal from said line deflection circuit, said gate means also having an output terminal for generating the gate pulses for said coincidence detector and said second phase discriminator.