The RTCDTMFSender interface's toneBuffer property returns a string containing a list of the DTMF tones currently queued for sending to the remote peer over the RTCPeerConnection. To place tones into the buffer, call insertDTMF().

Tones are removed from the string as they're played, so only upcoming tones are listed.


var toneBuffer = RTCDTMFSender.toneBuffer;


A DOMString listing the tones to be played. If the string is empty, there are no tones pending.

Tone buffer format

The tone buffer is a string which can contain any combination of the characters that are permitted by the DTMF standard.

DTMF tone characters

The digits 0-9
These characters represent the digit keys on a telephone keypad.
The letters A-D
These characters represent the "A" through "D" keys which are part of the DTMF standard but not included on most telephones. These are not interpreted as digits. Lower-case "a"-"d" automatically gets converted to upper-case.
The pound/hash sign ("#") and the asterisk ("*")
These correspond to the similarly-labeled keys which are typically on the bottom row of the telephone keypad.
The comma (",")
This character instructs the dialing process to pause for two seconds before sending the next character in the buffer.

All other characters are unrecognized and will cause insertDTMF() to throw an InvalidCharacterError exception.

Using tone buffer strings

For example, if you're writing code to control a voicemail system by sending DTMF codes, you might use a string such as "*,1,5555". In this example, we would send "*" to request access to the VM system, then, after a pause, send a "1" to start playback of voicemail messages, then after a pause, dial "5555" as a PIN number to open the messages.

Settting the tone buffer to an empty string ("") cancels any pending DTMF codes.




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

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
toneBufferChrome Full support 27Edge Full support ≤79Firefox Full support 52IE No support NoOpera Full support YesSafari ? WebView Android Full support 4.4Chrome Android Full support 27Firefox Android Full support 52Opera Android Full support YesSafari iOS ? Samsung Internet Android Full support 1.5


Full support
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Compatibility unknown
Compatibility unknown

See also