RTCDTMFToneChangeEvent
Events sent to indicate that DTMF tones have started or finished playing. This interface is used by the tonechange event.
var RTCDTMFToneChangeEvent: {
prototype: RTCDTMFToneChangeEvent;
new (type: string, eventInitDict?: RTCDTMFToneChangeEventInit): RTCDTMFToneChangeEvent;
};