This circuit for AC loads was found in February 1976, Radio Electronics magazine. The triac is common, and the times are given by the 20 MΩ resistor and the 1 uF capacitor.
This circuit with JFET was obtained in a book on FETs of 1989. The circuit is still current since...
This circuit was obtained from National Semiconductor documentation from the 1990s. The circuit has a...
Found in 90s documentation from Analog Devices, this circuit employs operational amplifiers of the time....