PURPOSE: To enable the stabilization and automatic regulation of the operations following up various input conditions by using control circuits of a microcomputer, non-volatile memory, etc., to store the operation state at the time of a control data change into the non-volatile memory.

CONSTITUTION: The microcomputer 44 in the control circuit has a means of measuring the frequencies of synchronizing signals of input video signals and accessing the non-volatile memory 55 corresponding to the results of the analysis and a means of accessing the data corresponding to inputted data by using input means such as rotary switches 49, 50. The microcomputer outputs the data for control judged by the external data input and input signal frequencies and makes communication with an external measurement controller. The automatic frequency follow up is thereby executed without using a variable resistor and the monitor can be connected even to an automatic regulator by a simple interface. The stable control is executed even in the neighborhood of the threshold of the input signal frequencies; in addition, the prepn. of the different operation conditions at the same frequency and the selection of the contents thereof are possible.