Found in a 1964 Electronic Design, this circuit generates pulses based on an avalanche diode of the time. The circuit can be tested with modern equivalent components.
This circuit using an operational amplifier was found in old American documentation. It can be...
If the circuit oscillates, emitting sound, it is because the transistor is good. This simple...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...