Signal tone
steady periodic sound used to indicate a condition
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.
Begin with the source’s own compact description: “Signal tone” is steady periodic sound used to indicate a condition. The dossier treats that line as a proposition to test through Signal, tone and steady, not as a finished interpretation.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Aug 1, 2023. The linked authority identifier is Q1149761. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Signal tone” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.