Found in a 1968 Motorola manual, this DC circuit uses components from the era. The circuit fires in microsecond times. The Q3 transistor must be according to the controlled load.
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...