RTCDTMFSender: toneBuffer property

BaselineWidely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2020.

TheRTCDTMFSender interface's toneBuffer property returns a stringcontaining a list of theDTMF tones currently queued for sending to theremote peer over theRTCPeerConnection. To place tones into the buffer,callinsertDTMF().

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

Value

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

Exceptions

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

Tone buffer format

The tone buffer is a string which can contain any combination of the characters thatare 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 DTMFstandard but not included on most telephones. These arenot interpreted asdigits. 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 rowof the telephone keypad.
The comma (","): This character instructs the dialing process to pause for two seconds before sendingthe next character in the buffer.

Note:All other characters are unrecognized and will causeinsertDTMF() to throw anInvalidCharacterErrorDOMException.

Using tone buffer strings

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

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