This old common analog telephone circuit was found in 1967 American documentation. The circuit uses only passive components.
This noise limiter for low intensity signals was found in a 73 magazine for radio amateurs from the...
The circuit shown in the figure uses a programmable unijunction transistor (PUT) of the BRY39 type...
Used with old projector films, this circuit found in Signalite documentation from the 1980s,...