Found in old documentation, this circuit has only the most difficult component to obtain the PUT. The sensors are electrodes placed in the reservoir. The circuit directly controls an AC power load.
Found in American documentation from the 1970s, this circuit is intended for amplifying analog TV...
Photoelectric cells can be used as sensitive light sensors. However, the low voltage they generate...
This circuit was found in a 90s American documentation. The circuit uses still common components...