Central office (CO) dial tone, sometimes referred to as hard dial tone, is provided by the CO switch to a terminal device. When the dial tone is seized, the user is free to dial a telephone number. See also CO.
A low, steady tone in a telephone receiver indicating that a number may be dialed.
A buzzing or humming sound indicating to the user of a telephone that the line is open and a number may be dialed.
An audible signal indicating that a telephone set is connected to a telephone switching system that is available to process an outgoing call.
PBX dial tone, sometimes referred to as internal dial tone or soft dial tone, is provided to a PBX station indicating that the PBX switch is available.The user is then free to dial an internal PBX station number. If the target telephone number is an external number, the user must dial an access code in order to gain access to an external trunk connected to the public switched telephone network (PSTN). See also PBX and PSTN.The conventional access code is nine (9) in the United States and Canada, and zero (0) in most other countries.
Stutter, or stuttered, dial tone is dial tone interrupted by short, regular periods of silence, and is used by some centrex and PBX systems as a message indicator, typically indicating that a voice message has been deposited in a voice mailbox either integrated with or interfaced directly to the system. Stuttered dial tone also is often used to confirm that a feature, such as call forwarding, has been activated or deactivated. See also call forwarding, centrex, and PBX.