Found in documentation from the 1980s, this circuit is used for resistive loads (incandescent lamps). The triac must be equipped with a heat sink.
This circuit is from Popular Electronics of the 90's. It makes use of NO and NC sensors. The relay...
Based on TTL logic this circuit can vary both the frequency and the pulse width of a rectangular signal....
This circuit was found in an old English publication. The circuit makes use of general-purpose transistors....