This circuit was found in a 1980s American documentation. The data circuit has a low speed, according to the components used. Transistors support modern equivalents.
The frequency of the sound emitted by this circuit depends on the light intensity on the sensor....
This circuit is from a thyristor manual from On Semiconductor. It makes use of a PUT and a SCR...
This circuit uses only one NC75Z04 port from ON Semiconductor, but it can be implemented with...