Found in 80's Electronic Engineering, this circuit can tune the frequency to be rejected. The power supply must be symmetrical.
This is the old name given to flip-flops or biestable multivibrators. In fact, this is a 1967...
This circuit can measure audio output power up to 50 W. The circuit is wired to the output of an...
Used with infrared remotes at the time, this circuit was found in a 1991 RE Experimenter Handbook....