The UVTRON tube is an ultraviolet radiation sensor. In this circuit from Radio Electronics from April 1990 we have a flame detector.
This circuit of a 1978 American publication monitors a telephone line by triggering a relay. The...
Found in 1965 General Electric technical documentation, this half-wave circuit controls shunt type...
The power supply shown in the figure provides voltages between 0 and approximately 15 volts, with...