Found in 1965 Delco Radio documentation, this circuit uses transistors from that era. Modern equivalents can be used. The characteristics of the inductor were not given.
To control relays safely with double insulation through the parallel port, we suggest the circuit in...
This '80s circuit drives an infrared LED, producing a modulated signal. Modern higher power LEDs...
This small receiver for the medium wave range was found in Radio Electronics magazine from July...