Aastra Telecom 57I C53I manual Out-of-Band Dtmf, Dtmf Method, Silence Suppression

Network Configuration of the IP Phones

Advanced Network Settings

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.

DTMF Method

A feature on the IP phone allows you to select the DTMF method that the phone uses to send DTMF digits from the IP phone via INFO messages. You can set the DTMF method as Real-Time Transport Protocol (RTP), SIP info, or both.

You can configure the DTMF method on a global or per-line basis using the configuration files or the Aastra Web UI.

Silence Suppression

In IP telephony, silence on a line (lack of voice) uses up bandwidth when sending voice over a packet-switched system. Silence suppression is encoding that starts and stops the times of silence in order to eliminate that wasted bandwidth.

Silence suppression is enabled by default on the IP phones. The phone negotiates whether or not to use silence suppression. Disabling this feature forces the phone to ignore any negotiated value.

You can configure this parameter via the configuration files or the Aastra Web UI.

Configuring the IP Phones

41-001160-00, Rev 01 Release 2.0 4-59