This two-microphone amplifier was found in a April 1961 Radio Electronics Magazine. The circuit is powered by battery and has a 600-ohm line output.
This Salen-Key filter can use any operational amplifier and other frequencies can be obtained by...
This circuit can be adapted to be used in a follow the line robot. It was found in the May 1962...
The circuit in the figure uses two of the 4001's four gates to trigger a relay in a timed manner. The...