Found in Ferranti's 1968 documentation, this circuit uses a Darlington photo transistor to drive a 12V relay. The circuit can be implemented with modern equivalent components.
The LM567 is a PLL tone decoder that can also be used as a double oscillator as shown in the...
Originally designed to analyze the shape of light pulses from a flash for photographic...
This interesting control circuit was found in an Electronics Now from 1988. Through it we can...