This circuit is from a Fairchild digital clock module shown in the March 1977 issue of Radio Electronics magazine. The circuit required a few external elements, including a common transformer.
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...