dial tone
Noun
Meaning
English Wikipedia has an article on:dial toneWikipedia
dial tone (plural dial tones)
A telephony signal, usually in the form of a sound, used to indicate that the telephone exchange is working, has recognized an off-hook, and is ready to accept a call.
Synonyms
Examples
Left alone with the dial tone... excuse me, operator, why is no one listening?
The PBX does not offer dial tone to the calling extension: it only detects on-hook or off-hook status.
It had the older, traditional Bell System 600 Hz+120 Hz dial tone.
When a user picked up the telephone handset, the resulting line loop operating the user's line relay caused the exchange to connect the user's telephone to an originating sender, which returned the user a dial tone.