A signal tone or signalling tone is a steady or pulsating
periodic signal typically in the frequency range of
sound
In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the br ...
for indicating a condition,
communication protocol
A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer science), sem ...
state, or serve as an audible warning. It may be composed of multiple frequency components, or could be a
pure tone
In psychoacoustics, a pure tone is a sound with a sinusoidal waveform; that is, a sine wave of constant frequency, phase-shift, and amplitude.
By extension, in signal processing a single-frequency tone or pure tone is a purely sinusoidal signal ...
.
In telephone systems, signaling tones are used as
call progress tones for
in-band
In telecommunications, in-band signaling is the sending of control information within the same band or channel used for data such as voice or video. This is in contrast to out-of-band signaling which is sent over a different channel, or even o ...
indications to subscribers or operators. Certain telephone switching systems used tones, in-band or out-of-band, for
signaling on trunks.
Typical well-known call progress tones are
dial tone
A dial tone (dialling tone in the UK) is a telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone, when an off-hook condition is detected. It indicates that the exchange is ...
,
ringing tone,
busy tone, and the
reorder tone.
A loud stutter tone is used to alert subscribers of a handset left off-hook, effectively disabling the circuit for receiving calls.
Telephone service subscribers may subscribe to services, such as call forwarding, which may indicate function by a stutter dial tone.
See also
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Musical tone
Traditionally in Western classical music, Western music, a musical tone is a steady periodic function, periodic sound. A musical tone is characterized by its duration (music), duration, pitch (music), pitch, amplitude, intensity (or loudness), an ...
*
Dual-tone multi-frequency signaling
Dual-tone multi-frequency (DTMF) signaling is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and Automatic telephone exchange, switching center ...
(DTMF)
*
Signaling (telecommunications)
In telecommunications, signaling is the use of signals for controlling communications. This may constitute an information exchange concerning the establishment and control of a telecommunication circuit and the management of the network.
Clas ...
References
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Telephony signals