Answer tone

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Feature of wireline modems

title: "Answer tone" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["modems"] description: "Feature of wireline modems" topic_path: "general/modems" source: "https://en.wikipedia.org/wiki/Answer_tone" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Feature of wireline modems ::

Answer tone is a feature of wireline modems. |filename = ANSam.wav |title = ITU-T Answer Tone |description = Typical 2,100Hz answer tone with phase reversals and amplitude modulation. |pos=right}}

The answer tone is the first signal sent by the answering modem after the billing delay. In its most basic form, it is a single continuous tone with a frequency of 2100 Hz (or 2225 Hz for Bell modes). It is the tone heard by the caller after dialing the number.

The plain 2100 Hz tone is meant to disable echo suppressors on international trunk connections. It may include 180° phase reversals at intervals of 450 ms to disable network echo cancellers. It may also be amplitude modulated by a 15 Hz signal to indicate ITU-T V.8 capability.

References

  • {{cite book | last = Mueller | first = Scott | title = Upgrading and Repairing PCs | edition = 6th |date=September 1996 | publisher = QUE | isbn = 0-7897-0825-6 | pages = 482 – 483 | chapter = Communications and Networking
  • {{cite book | last = Bigelow | first = Stephen J. | title = PC Technician's Troubleshooting Pocket Reference | edition = 2nd | date = October 13, 2000 | publisher = McGraw-Hill Professional | isbn = 0-07-212945-X | pages = 287 – 289 | chapter = Modem Troubleshooting | url-access = registration | url = https://archive.org/details/pctechnicianstro0000bige/page/287

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::

modems