Assertion: hook tone | /r/MadeOf | a superposition of tones
Facets:
Source sentences:
text: The off-hook tone in exchanges of the North American Numbering Plan consists of a superposition of tones with the frequencies 1400 Hz, 2060 Hz, 2450 Hz, and 2600 hertz, played at a cadence of 0.1 s on and 0.1 s off.