Loudspeaker A transducer which converts electrical energy to sound.
Piezo Transducer A transducer which converts electrical energy to sound
A NOT gate can only have one input. The o on the output means not. The output of a NOT gate is the inverse (opposite) of its input, so the output is true when the input is false. A NOT gate is also called an inverter.
Galvanometer A very sensitive meter used to measure tiny currents, usually 1mA or less.