This circuit from a 1966 General Electric manual makes use of an SCS. The time is given by the emitter capacitors of the unijunction transistor.
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...