This old circuit, from the 80s, was found in American documentation. The circuit uses dual gate FETs (MOSFETs) and has no data on the coils used.
The purpose of this circuit is to adapt a common speaker to function as a microphone. The circuit is...
This amplifier circuit for listening was found in a book by Hugo Gernsback from 1960. The...
The presented circuit uses an optocoupler to trigger a triac. We found it in a Popular Electronics from...