---
title: "Signal tone"
chunk: 1/1
source: "https://en.wikipedia.org/wiki/Signal_tone"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T11:53:37.284385+00:00"
instance: "kb-cron"
---

A signal tone or signalling tone is a steady or pulsating periodic signal typically in the frequency range of sound for indicating a condition, communication protocol state, or serve as an audible warning.  It may be composed of multiple frequency components, or could be a pure tone.
In telephone systems, signaling tones are used as call progress tones for in-band 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, 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 ==
Musical tone
Dual-tone multi-frequency signaling (DTMF)
Signaling (telecommunications)


== References ==