In the figure we have the way to obtain 500 gain from a FET. FETs can be BF245 or MPF102. The circuit is from the 1977 National Semiconductor FET Data Book. Power supply depends on the application.
This code switch was found in a 1990 Electronics Handbook. It can be mounted with BC558...
In this application we use an additional input circuit to enable the logic command with keys,...
This circuit was suggested by Signetics in 1980s documentation. The circuit makes use of the...