Table of Contents
Advertisement
DTMF does not work.
You tried to check your voice mail using the DTMF pad, but the connection could
not be established. There are three different protocols used for the transmission of
DTMF data, but only two of these are supported by Linphone (SIP INFO and RTP
rfc2833). Check with your provider whether it supports one of these. The default
protocol used by Linphone is rfc2833, but if that fails you can set the protocol to
SIP INFO in Preferences → Network → Other. If it does not work with either of
them, DTMF transmission cannot be done using Linphone.
8.7 Glossary
Find some brief explanation of the most important technical terms and protocols men-
tioned in this document:
VoIP
VoIP stands for voice over Internet protocol. This technology allows the transmis-
sion of ordinary telephone calls over the Internet using packet-linked routes. The
voice information is sent in discrete packets like any other data transmitted over
the Internet via IP.
SIP
SIP stands for session initiation protocol. This protocol is used to establish media
sessions over networks. In a Linphone context, SIP is the magic that triggers the
ring at your counterpart's machine, starts the call, and also terminates it as soon as
one of the partners decides to hang up. The actual transmission of voice data is
handled by RTP.
RTP
RTP stands for real-time transport protocol. It allows the transport of media streams
over networks and works over UDP. The data is transmitted by means of discrete
packets that are numbered and carry a time stamp to allow correct sequencing and
the detection of lost packages.
DTMF
A DTMF encoder, like a regular telephone, uses pairs of tones to represent the
various keys. Each key is associated with a unique combination of one high and
one low tone. A decoder then translates these touch-tone combinations back into
numbers. Linphone supports DTMF signalling to trigger remote actions, such as
checking voice mail.
164
KDE User Guide
Advertisement
Table of Contents
