This alarm circuit was found in April 1975 Radio Electronics magazine. The circuit uses a 12 V power supply and relay but can be modified to work with other voltages.
This 1-transistor oscillator circuit was found in the March 1965 Radio Electronics magazine. The...
In the figure we have a way to adapt a phone obtained to the output of a common amplifier. The...
This sensitive touch key appears on this website from other sources. This version was taken from a...