Abstract: A power throw circuit is provided within a keyboard-equipped apparatus such as an electronic calculator, an electronic timepiece etc. for determining whether a battery or batteries are connected between supply terminals therefor, whereby a power supply controller is not enabled to disconnect said power supply unless a power throw detection signal is developed from the power throw circuit. In response to the occurrence of the power throw detection signal from the power throw circuit power energy is automatically supplied from the power source to a power utilization circuit. In a preferred form, once the power utilization circuit has been enabled, and placed into the stable condition, the power throw detection circuit will no longer have any influence on the utilization circuit. In such stable conditions, the subsequent actuations of any key of a keyboard can control the power supply from the power source to the power utilization circuit.

Abstract: A system clock generator for use in a CMOS LSI chip includes a clock control signal generator for developing a control signal in response to a clock generating instruction or inhibition instruction; and a clock generator supplied with the output of an oscillator for developing a basic clock of a desired waveform for supply to the system, wherein the basic clock is developed or inhibited when the control signal is supplied from the clock control signal generator.