Found in the September 1972 issue of Radio Electronics magazine, this signal injector is based on the HEP580. The circuit is powered by two batteries and its frequency is basically given by C1.
Frequencies up to just over 100 kHz can be obtained with an oscillator based on one of the four...
This circuit, found in a Popular Electronics from 1992, is based on an oscillator and a crystal...
This is a discrete equivalent version of an open collector TTL gate. What we have is an inverter...