This two-microphone amplifier was found in a April 1961 Radio Electronics Magazine. The circuit is powered by battery and has a 600-ohm line output.
This spinner (see CB18894E) uses only an operational amplifier that must be powered by a...
The incidence of light in the LDR causes this circuit to start operating, emitting a sound whose...
This circuit is from American documentation. The components used are still common. The power...