This circuit was suggested by General Electric in a 1969 documentation. The transistors are of the time and the power supply is not given. Note the high supply voltage.
This circuit was obtained from an English publication from the 70's. The circuit is still current for...
This circuit was found in a 1979 magazine. We can use any JFET like MPF102 or BF245. The relay is 12 V...
Found in Motorola documentation from the 90s, this circuit can be implemented with current...