Found in a 1967 General Electric SCR manual, this circuit can be used to protect a load by switching in case of excess current. R1 determines the trigger current.
This circuit is from a Popular Electronics from the 90s. The integrated circuit admits equivalents...
This very interesting project was obtained in a 1980 publication. It consists of a device that is...
This circuit beeps when the sensor is triggered by the opening of the freezer door or other...