Found in old documentation, this circuit can use modern equivalent components. The signal has good strength thanks to the use of a power transistor. The Q1 transistor is a unijunction of the time.
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...