This simple neon lamp oscillator produces a 140 Hz, 40 V peak-to-peak signal. The frequency is given by the capacitor that can have its value changed. Note the high supply voltage.
Found in a 1967 Electronics World, this circuit can use any modern equivalent FET. Observe the...
This 1967 Philips circuit recognizes a light signal (visible or infrared) modulated by tone. The...
The circuit of the figure serves the same purpose as the previous one (CB5057E), but has a...