Nokia C3-01 - Does Nokia Series 40 VoIP implementation support DTMF signaling?

Yes, Nokia Series40 VoIP implementation supports sending of the DTMF (Dual-Tone Multifrequency) digits. The DTMF digits can be sent via the Options > Send DTMF command when the SIP VoIP call is active.

Series 40 supports sending of the DTMF digits in out-band. In which the signaling the DTMF digits are sent as RTP payload data as specified in IETF RFC 2833.