The circuit shown was found in the February 1994 issue of Electronics Now magazine. The circuit records messages for a few seconds and plays them back as keys are selected.
This 80's circuit has been winning. It is a 1 000 gain sample and hold circuit and an offset...
The purpose of this 1-transistor amplifier is to allow the use of a milliammeter in an application...
We found this circuit in an old General Electric documentation. In fact, PUTs are not common...