| 摘要 |
PURPOSE:To attain long service life of a battery by connecting two resonance circuits having a resonance frequency different slightly to one crystal oscillator in parallel and switching alternately them with an output of a digital logical circuit. CONSTITUTION:A microcomputer 2 is operated by a battery power supply 3, a signal S1 is outputted only at signal transmission and outputs either a signal S2 or S3 depending on the state of a sensor 1. A transistor Q1 is turned on when the signal S1 is at a low level and gives power to a high frequency oscillation circuit. Two capacitors are connected respectively in parallel with a common inductance of a crystal oscillator 4 via switching diodes D1, D2. When the signal S2 is at a low level, the switching diode D1 is turned on, the oscillation circuit is oscillated at a frequency f1 and when the signal S3 is at a low level, the switching diode D2 is turned on and a frequency f2 is oscillated. |
