Method and apparatus for establishing a servicing mode of an electronic

Abstract

In controlling an electronic apparatus, such as, a color television receiver, of the type having signal processing circuits which are individually adjustable in accordance with respective control signals provided by a microcomputer or central processing unit (CPU) in response to data corresponding to predetermined or standardized conditions of the adjustable circuits and which are stored in a non-volatile memory along with a secret code, operating keys selectively actuable to provide input data to the CPU for representing an externally applied code and, in a servicing mode of the receiver, for rewriting the data in the memory and thereby changing the standardized conditions of the adjustable circuits, and inner bus lines connecting the CPU to the adjustable circuits, the non-volatile memory and the operating keys; a standby power supply provides electric power to the CPU at a time when operating keys are actuated for inputting data representing an externally applied code to the CPU, a main power supply is turned on for supplying power to the adjustable circuits and thereby causing the receiver to display a color image, and the servicing mode of the receiver is established only when the externally applied code coincides with the stored secret code and the turning on of the main power supply is effected within a predetermined period after the externally applied code has been made to be coincident with the stored secret code.