This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is 1000 M ohm.
Epson SG 8018 Epson Crystal Programmable Oscillators Available from Mouser Electronics, these...
When the lights turns off this circuit will produce a sound like a cricket. When the lights are...
This circuit appears elsewhere on the site. The circuit shown is from an American 1980s...