We found this circuit in a 1973 publication. The circuit lets frequencies below 480 kHz pass through with an output impedance of 1k. The circuit can be implemented with current operational.
This TTL heads or tails circuit was found in the July 1973 Radio Electronics magazine. The LEDs...
Of course, with a change in the cable length, the frequency can be changed as long as it is within...
This low-frequency sine wave oscillator was found in the December 1995 issue of Electronics Now...