- Utility frequency (Wikipedia)
The utility frequency, (power) line frequency (American English) or mains frequency (British English) is the nominal frequency of the oscillations of alternating current (AC) in a wide area synchronous grid transmitted from a power station to the end-user. In large parts of the world this is 50 Hz, although in the Americas and parts of Asia it is typically 60 Hz. Current usage by country or region is given in the list of mains electricity by country.
- Phonograph (Wikipedia)
A phonograph, later called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910), and since the 1940s a record player, or more recently a turntable, is a device for the mechanical and analogue reproduction of recorded sound. The sound vibration waveforms are recorded as corresponding physical deviations of a helical or spiral groove engraved, etched, incised, or impressed into the surface of a rotating cylinder or disc, called a “record”. To recreate the sound, the surface is similarly rotated while a playback stylus (or “needle”) traces the groove and is therefore vibrated by it, faintly reproducing the recorded sound. In early acoustic phonographs, the stylus vibrated a diaphragm that produced sound waves coupled to the open air through a flaring horn, or directly to the listener’s ears through stethoscope-type earphones.