This alarm with NO and NC sensors was found in the January 1975 Radio Electronics magazine. The circuit emits a powerful sound that depends on the output transistor.
We found this circuit in an old English publication. Transistors are general purpose and the block...
This simple circuit was found in the Spanish magazine “Todo Electronica”, in an edition of 1996....
This circuit operates at a voltage of 1.3 V from a single mercury cell. We found in an old...