what are dtmf tones
DTMF tones are used during a call to signal to a far-end device; these signals maybe for navigating a menu system, entering data, or for other types of manipulation. They are processed differently from the DTMF tones sent during call setup as part of the call control. TDM interfaces on Cisco devices support DTMF by default. Cisco VoIP dial-peers do not support DTMF relay by default and require DTMF relay capabilities to be enabled.