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.
Using the LM3914, this circuit is suitable for benchtop experiments. It was found in the March 1995...
This very sensitive circuit works almost like an electroscope. The FET can be the BF245 and it...
This 50's receiver includes an amplifier stage with a transistor complementary to the CK722, in...