This is a different circuit for a component from the past, the zirconium arc lamp used in projectors. The circuit is from an August 1972 Radio Electronics magazine.
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...