This circuit was found in a 1967 US documentation. It shows how to build a gain control by digital signals. The circuit can be used as a shield. FET can be a modern equivalent.
This sensitive circuit was found in the June 1995 Electronics Now magazine. R1 can be from 10k to 1M...
This is a basic inverter circuit for a 70 kHz crystal. We found it in an old documentation using an...
This low-pass filter was found in an American publication from the 80's. The circuit uses an...