from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A low, steady tone in a telephone receiver indicating that a number may be dialed.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. 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.
Sorry, no etymologies found.