PURPOSE: To prevent a distorted image from being displayed by switching a switch circuit according to the scan mode by means of a discrimination signal from a mode-switching device.
CONSTITUTION: When the television scanning mode is selected, the TS switch of a mode-switching device 13 is turned on and a discrimination signal 14 indicating the television scanning mode is delivered to a switch circuit 12. Then the switch circuit 12 opens the gate to send out an electronic image signal from a video amplifier 10 to an external monitoring device. When a mode other than the television scanning mode is selected and the SS1 switch of the mode-switching device 13 is supposed to be turned on, a discrimination signal 14 indicating this is delivered to the switch circuit 12. Then the switch circuit 12 decreases an electronic image signal from the video amplifier 10 to the grounding potential level thereby delivering a black level signal to the external monitoring device. As a result, the CRT picture screen of the external monitoring device becomes dark thereby preventing the distorted image from being displayed.
TOYODA KAZUTOKI
OONO TERUAKI
HITACHI NAKA SEIKI KK