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.

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

InvalidCharacterError DOMException

Thrown if a character is not a DTMF tone character (0-9, A-D, # or ,).

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.

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.

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

tbd

• WebRTC API
• Using DTMF with WebRTC
• RTCDTMFSender.insertDTMF()
• RTCPeerConnection
• RTCDTMFSender
• RTCRtpSender