Matrix Sparsh VP110 User Manual

198 Matrix SPARSH VP110 User Guide
DTMF
DTMF (Dual Tone Multi-frequency), better known as touch-tone, is used for telecommunication signaling over
analog telephone lines in the voice-frequency band. DTMF is the signal sent from the IP phone to the network,
which is generated when pressing the IP phone’s keypad during a call. Each key pressed on the IP phone
generates one sinusoidal tone of two frequencies. One is generated from a high frequency group and the other
from a low frequency group.
The DTMF keypad is laid out in a 4 × 4 matrix, with each row representing a low frequency, and each column
representing a high frequency. Pressing a digit key (such as '1') will generate a sinusoidal tone for each of two
frequencies (697 and 1209 hertz (Hz)).
DTMF Keypad Frequencies:
Three methods of transmitting DTMF digits on SIP calls:
• RFC 2833 -- DTMF digits are transmitted by RTP Events compliant to RFC2833.
• INBAND -- DTMF digits are transmitted in the voice band.
• SIP INFO -- DTMF digits are transmitted by SIP INFO messages.
RFC 2833
DTMF digits are transmitted using the RTP Event packets that are sent along with the voice path. These packets
use RFC 2833 format and must have a payload type that matches what the other end is listening for. The payload
type for RTP Event packets is configurable. IP phones default to 101 for the payload type, which use the definition
to negotiate with the other end during call establishment.
The RTP Event packet contains 4 bytes. The 4 bytes are distributed over several fields denoted as Event, End bit,
R-bit, Volume and Duration. If the End bit is set to 1, the packet contains the end of the DTMF event. You can
configure the sending times of the end RTP Event packet.
INBAND
DTMF digits are transmitted within the audio of the IP phone conversation. It uses the same codec as your voice
and is audible to conversation partners.
SIP INFO
DTMF digits are transmitted by the SIP INFO messages when the voice stream is established after a successful
SIP 200 OK-ACK message sequence. The SIP INFO message is sent along the signaling path of the call. The SIP
INFO message can support transmitting DTMF digits in three ways: DTMF, DTMF-Relay and Telephone-Event.
1209Hz 1336Hz 1447Hz 1633Hz
697Hz 1 2 3 A
770Hz 4 5 6 B
852Hz 7 8 9 C
941Hz * 0 # D

Matrix Sparsh VP110 Specifications

General

Brand	Matrix
Model	Sparsh VP110
Category	IP Phone
Language	English