CRYSTAL MICROPHONE

A phonograph pickup in which movements of the needle in the record groove cause deformation of a piezoelectric crystal, thereby generating an audio-frequency output voltage between opposite faces of the crystal. Also known as piezoelectric pickup.

A steel bar with projections or indentations to increase mechanical bonding; used to reinforce concrete.

[ENG ACOUS] Loudspeaker in which the mechanical forces result from the deformation of a material having magnetostrictive properties.

1. An iron or steel bar that is usually bent and has a wedge-shaped working end; used as a lever and for prying. 2. A device or action that in effect places a high overload on the actuating element of a circuit breaker or other protective device, thus triggering it.

An instrument for measuring rotational speed by measuring the output voltage of a generator driven by the rotating unit.

A device that transforms heat energy first into sound energy and then into electrical power, without the use of moving mechanical parts.

Circuit containing inductance or capacitance, or both, and resistance, connected so that a voltage impulse will produce an output current which periodically reverses or oscillates.

An instrument which weighs an object by measuring the change in resistance caused by the elastic deformation of a mechanical element loaded with the object.

1. The ratio of radiated sound intensity at a remote point on the principal axis of a loudspeaker or other transducer, to the average intensity of the sound transmitted through a sphere passing through the remote point and concentric with the transducer; the frequency must be stated.
2. The ratio of the square of the voltage produced by sound waves arriving parallel to the principal axis of a microphone or other receiving transducer, to the mean square of the voltage that would be produced if sound waves having the same frequency and mean-square pressure were arriving simultaneously from all directions with random phase; the frequency must be stated.

Limiting the maximum output voltage of a vacuum tube circuit by driving the grid beyond cutoff.