This circuit was found in Ferranti's 1974 transistor manual. The transistors are from the period and the frequencies generated are between 50 Hz and 2 kHz.
This circuit was found in old American documentation. Transistor is general purpose and relay is...
This simple alarm with latching uses a relay as the main element. The circuit is from a Radio...
This circuit is from an Italian publication called Fare Elettronica from 1987. What we have is an...