This circuit was originally intended to operate with a solar source for experiments. Transistors are general purpose, and the output current is relatively low.
This circuit mimics the dialing of an old telephone. The reproduction is made in a loudspeaker and the power...
This filter is from a 1977 manual. The integrated circuit is 741. The frequency is given by f = 1...
This simple optical alarm circuit was found in the 1991 Electronics Experimenter Handbook. The...