We find this oscillator in a 1980s documentation. The frequency depends on the crystal and the transistor used must be able to oscillate at the desired frequency.
This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and...
This circuit can be used to drive relays, solenoids, motors and other loads according the...
This circuit is based on the small keychain that responded to the sound of a whistle and were...