This circuit makes use of a low impedance microphone. The relay is according to the supply voltage which can be between 9 and 15 V. The operational gain is approximately 100.
This simple circuit is intended to test integrated circuits 555 and 741 in 8-pin DIL enclosures. In both...
This circuit was obtained from a Radio Electronics magazine from June 1969. The circuit uses a...
This additional bell circuit was found in the February 1994 Electronics Now magazine. The...