With the configuration shown in the figure, we have the relay being activated when the microphone picks up a sound and shutdown when the X1 reset sensor is activated.
This circuit was obtained in an old Argentine publication, using germanium transistors and...
This very low resistance meter was found in the February 1995 issue of Electronics Now magazine. The...
Using a CA3130 operational amplifier, this circuit was found in an English publication from 1977....