This circuit takes advantage of the noise generated at the reverse biased junction of a germanium diode. Other types of diodes can be used. The signal is weak.
Found in an English Maplin magazine in 1983, this circuit has an RIAA equalization. We suggest its...
We found this circuit in a 1991s PE Hobbyst Handbook. The circuit fires 10 LEDs that can control...
This alarm with NO and NC sensors was found in the January 1975 Radio Electronics magazine. The...