Using a varactor or varicap, this 1969 Electronics World circuit has a modulation range from 75 kHz to 52 MHz. Modern equivalent components can be used.
We found this decoder in a 1966 General Electric publication. It makes use of general purpose...
Another alternate action switch that uses a NAND Schmitt Gate [4093 IC] is shown here. The...
This filter operates in the “opposite” way to the previous one (CIR8814), cutting all signals...