Configuring Basic Features
93
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:
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
There are 3 common methods of transmitting DTMF digits on SIP calls:
RFC 2833 – DTMF digits are transmitted by RTP Events compliant to RFC 2833.
INBAND – DTMF digits are transmitted in the voice band.
SIP INFO – DTMF digits are transmitted by the SIP INFO messages.
The method of transmitting DTMF digits is configurable on a per-account basis.
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 the RTP Event packets
is configurable. The IP phone often defaults to 101 for the payload type, which uses your
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 number of times for
the IP phone to send the RTP Event packet with End bit set to 1. The number of times is 3
by default.
Summary of Contents for VP530 IP
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Page 4: ......
Page 12: ......
Page 111: ...Configuring Basic Features 99...
Page 153: ...Configuring Advanced Features 141...
Page 171: ...Configuring Security Features 159...
Page 182: ...Administrator s Guide for VP530 IP Video Phone 170 Phonebook on page 266...
Page 183: ...Resource Files 171...
Page 194: ...Administrator s Guide for VP530 IP Video Phone 182 3 Click OK to confirm the resetting...
Page 195: ...Troubleshooting 183...
Page 344: ...Administrator s Guide for VP530 IP Video Phone 332...