Vertical Scanning Generator

an electronic device for vertical image scanning. Vertical scanning generators are used in television cameras and receivers for cophasal and synchronous deflection of the electron beams in camera tubes and kinescopes. In television, electromagnetic deflection of the electron beam is usually used for vertical scanning. It is created by an electric current flowing in the deflection coils; the current varies linearly according to a sawtooth law. Current of this type is produced by a vertical scanning generator, the main parts of which are a self-excited oscillator of short-duration square pulses with a repetition frequency of 50-60 hertz, a circuit or stage for the formation of the control (sawtooth) voltage, and a scanning output stage.

A blocking oscillator (less often, a multivibrator), to which the frame synchronizing pulses contained in a composite picture are fed, is most frequently used as the square-pulse oscillator. The control voltage is formed in an electron-tube stage or a transistor with a discharging circuit. Scanning output stages with a transformer output, to which the vertical deflection coils are connected, are the most common. The control voltage is fed to such an output stage in the form of a parabolic pulse.