1. (n.) One who, or that which, regulates.

2. (n.) A contrivance for regulating and controlling motion, as: (a) The lever or index in a watch, which controls the effective length of the hairspring, and thus regulates the vibrations of the balance. (b) The governor of a steam engine. (c) A valve for controlling the admission of steam to the steam chest, in a locomotive.

3. (n.) A clock, or other timepiece, used as a standard of correct time. See Clock.

4. (n.) A member of a volunteer committee which, in default of the lawful authority, undertakes to preserve order and prevent crimes; also, sometimes, one of a band organized for the commission of violent crimes.

attenuator audio-frequency tube ballast regulator ballast tube beam-switching tube convertor current regulator damper detector discriminator doubler ear trumpet electronic hearing aid focus tube generator hard-of-hearing aid hearing aid iconoscope inverter limiter local-oscillator tube megaphone mixer tube modulator multiplier multipurpose tube multivibrator oscillator output tube phase inverter picture tube power tube preamp preamplifier pulse generator radio-frequency tube receiving tube rectifier tube regulator repeater speaking trumpet stethoscope transducer transistor hearing aid trigger tube vacuum-tube hearing aid