call.sendDTMF() sends DTMF tones during a call. It can only be used to send tones while already in a call - not to place a call.
Tone duration is 300 ms, with 100 ms pause between each tone.
call.sendDTMF(sequence)
Nothing.
None.
call.sendDTMF("12p34") sends DTMF tones for 1 and 2, pauses 2 seconds, then sends tones for 3 and 4.
The Chrome browser can send DTMF tones inband, as audio tones in the media stream.
Other browsers are not capable of that, but need to send DTMF tones outband, as SIP INFO messages.
call.sendDTMF() will send DTMF tones inband in Chrome and outband on other browsers.
To send DTMF tones both inband and outband on Chrome set wrtc.adv.dtmfInfo=true