The UTStarcom F3000 WiFi Phone doesn’t work on Skype, but it does the next best thing, SIP. It supports SDP, RTP/RTCP, RFC2833/inband DTMF, and supports the G.711 and G.729 codecs.

DTMF was developed to cure these ills and open up a wide range of potentially lucrative services. AT&T had been working on push button dialing since the early 1940s, first using mechanical systems ...

In both cases, the DTMF tones travel on the same channel, or band, as the voice conversation, one-sided though it may be. In-band signaling works in radio transmissions, too, as a way for one ...