This highly sensitive light sensor was found in a 1970 General Electric documentation. The circuit can use the 2N2646 for the UJT and the phototransistor can be of any type.
This 1967 Philips circuit recognizes a light signal (visible or infrared) modulated by tone. The...
This circuit turns on an old cassette recorder when the telephone rings, thus enabling the...
This is the receiver for the previous circuit transmitter. Similarly, no information about the...