Found in documentation from the 90s, this circuit was used in communications receivers of the time. MOSFET is a component of the time, uncommon today.
This amplifier with gain control was obtained in a documentation from Signetics of the 80's....
The commercial MT2B receiver manufactured in Japan in the 1960s had a listening device only and...
This negative ion generator was found in a 90s Popular Electronics. The autotransformer can be an...