This circuit was found in a Popular Electronics from the 90s. It is based on components still common today and an optical coupler for the triac. The sensor is a thermistor.
The CMOS 4046 integrated circuit is not very common today, consisting of a very efficient PLL for...
This circuit turns on an old cassette recorder when the telephone rings, thus enabling the...
This circuit can be used in panel signaling with common incandescent lamp. The lamp will flash at a...