This circuit was found in an American documentation from the 90s. It consists of a variable with a triac in which the load current can be controlled, monitored by an ammeter.
Disabling this circuit from a 2002 documentation can only be done by pressing 4 keys in a correct...
This circuit was found in a 1979 magazine. We can use any JFET like MPF102 or BF245. The relay is 12 V...
This circuit was obtained in a 90’s documentation. The operational amplifiers are from that time....