Aastra Telecom SIP 57I - Manual (Page 191)

Global SIP Settings
41-001160-00, Release 2.1, Rev 04 4-67
Configuring Network and Session Initiation Protocol (SIP) Features
Configuring the IP Phones Silsupp is used to enable or disable silence suppression. Voice Activity Detection
(VAD) on the IP phones is used to determine whether each individual packet
contains useful speech data. Enabling silsupp results in decreased network
bandwidth, by avoiding sending RTP packets for any frame where no voice
energy was detected by the VAD.
You must enter the values for this feature in list form as shown in the following
example:
payload=8;ptime=10;silsupp=on; payload=0;ptime=10;silsupp=off
The valid values for creating a Codec preference list are as follows.
Customized Codec Settings
You can specify a customized Codec preference list on a global-basis using the
configuration files or the Aastra Web UI.
Out-of-Band DTMF
The IP phones support out-of-band Dual-Tone Multifrequency (DTMF) mode
according to RFC2833. In the Aastra Web UI, you can enable or disable this
feature as required. The "out-of-band DTMF" is enabled by default.
In out-of-band mode, the DTMF audio is automatically clamped (muted) and
DTMF digits are not sent in the RTP packets.
You can configure out-of-band DTMF on a global-basis using the configuration
files or the Aastra Web UI.
Attribute Value
payload 0 for G.711 u-Law
8 for G.711 a-Law
18 for G.729a
ptime (in milliseconds) 5, 10, 15, 20.......90
silsupp on
off