The RTCDTMFToneChangeEvent interface represents events sent to indicate that DTMF tones have started or finished finished playing. This interface is used by the tonechange event.


In addition to the properties of Event, this interface offers the following:

RTCDTMFToneChangeEvent.tone Read only
A DOMString specifying the tone which has begun playing, or an empty string ("") if the previous tone has finished playing.


Returns a new RTCDTMFToneChangeEvent. It takes two parameters, the first being a DOMString representing the type of the event (always "tonechange"); the second a dictionary containing the initial state of the properties of the event.


Supports the methods defined in Event. There are no additional methods.


This snippet is derived loosely from the full, working example you'll find in "When a tone finishes playing" in Using DTMF with WebRTC. It appends each tone to a display box as it's played, and, once all tones have been sent, re-enabled a previously-disabled "Send" button, allowing the next DMTF string to be entered.

dtmfSender.addEventListener("change", function(event) {
  if (event.tone !== "") {
    dialStringBox.innerText += event.tone;
  } else {
    sendDTMFButton.disabled = false;
}, false);


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

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) 52 (52) No support (Yes) ?
Feature Android Chrome for Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? ? (Yes) 52.0 (52) No support ? ?

See also

Document Tags and Contributors

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