Gittersperrschaltung

A first grid muting circuit for a monitor display for smooth muting operation of a muting circuit portion to provide a stable picture to a viewer can be favorably applied to a monitor circuit by a microcomputer for supplying a muting signal to blocks per corresponding modes, a contrast muting circuit portion for muting the muting signal to a predetermined level, a video circuit for outputting the muted contrast signal as a video signal, a first grid drive portion for driving a first grid circuit, and the first grid circuit for outputting a first grid signal for controlling a cathode ray tube to a vertical blanking circuit in accordance with a control signal of the first grid drive portion. The first grid muting circuit further has a plurality of switches for selectively switching a positive power supply voltage in accordance with the muting signal of the microcomputer to output the switched positive power supply voltage, and resistors for variably adjusting a negative power supply voltage in accordance with a predetermined variable resistance value to output the adjusted negative power supply voltage, thereby minutely controlling the operation of a muting circuit portion to provide the stable picture.