This circuit has visual and audible status indication using an oscillator. The circuit is from a Radio Electronics magazine from June 1991.
This circuit was suggested by Philips in 1967 documentation. The circuit receives modulated light and has...
This circuit is from a 1965 Electronic Design. The transistors may be general purpose and the...
Hughes suggests this circuit in a 1968 documentation. The circuit uses old transistors that can be...