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The read-only property RTCDTMFToneChangeEvent.tone returns the DTMF character which has just begun to play, or an empty string (""). if all queued tones have finished playing (that is, RTCDTMFSender.toneBuffer is empty).


 var tone = RTCDTMFToneChangeEvent.tone;


This example establishes a handler for the tonechange event which updates an element to display the currently playing tone in its content, or, if all tones have played, the string "<none>".

dtmfSender.ontonechange = function( ev ) {
  let tone = ev.tone;
  if (tone === "") {
    tone = "&lt;none&gt;"

  document.getElementById("playingTone").innerText = tone;


Specification Status Comment
WebRTC 1.0: Real-time Communication Between Browsers
The definition of 'RTCDTMFToneChangeEvent.tone' in that specification.
Candidate Recommendation Initial specification.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes52 No Yes ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support ? Yes Yes52 ? ? ?

See also

Document Tags and Contributors

 Contributors to this page: fscholz, Sheppy
 Last updated by: fscholz,