Abstract: 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.

Abstract: A mode detector of a multimode monitor comprising a band separation circuit for separating band of input vertical and horizontal frequencies to provide logic signals, a control signal generation circuit for providing mode control signals, and a mode control circuit for controlling each mode of the multimode monitor.According to the present invention, the vertical and horizontal sizes, the vertical and horizontal oscillating frequencies, the horizontal pin cushion and the like can be automatically controlled according to the mode of input frequencies by detecting the mode of the input frequencies in the control signal generation circuit and by providing the combined logic signals of the control signal generation circuit to the mode control circuit.