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SIP Operation Manual
Fax Settings
NOTE: When a fax tone is detected in a call, the gateway will automatically switch from voice mode to
fax mode. So fax settings will be temporarily applied to a specific port which detects fax tones, instead
of its default voice settings.
T.38: T.38 FAX relay function is the best choice fro reliable and efficient facsimile
transmission over network. It transmits and receives FAX waveform (relaying) over the
codec negotiated during call setup this bandwidth consumed is lowered. T.38 protocol
also supports redundancy to get better FAX quality.
Enable High Quality: To compensate possible loss of packet during transmission, this
function will send T.38 packet twice over network. It increases approximately double
bandwidth but offers good and reliable quality.
T.30: T.30 provides another choice for FAX over IP without compression. It transmit FAX
signal as voice thus uncompressed G.711 would be the choice. (G.726 also works but not
recommended). Due to this nature, T.30 always requires a SDP change (change of codec
within a session, SIP Re-Invite required) after FAX tone detected by the callee. This is a
key even to identify if T.30 works in a new environment.
FAX Jitter Buffer: Adjusts the jitter to receive fax packets. If the jitter range is too large, it
will delay fax transmission.
NOTE: When you send fax over an IP network it needs your network to support fax over IP functionality
(either T.38 or T.30). Please consult your Internet Telephony Service Provider for this setting.
Drop Inactive Call
This is used as a standard to determine whether or not to hang up the phone. The gateway will
hang up the phone automatically to avoid keeping the line engaged if the detected volume is below
the
Silence Detection Threshold
and the exceeds the
Drop Silent Call Timeout
.
Silence Detection Threshold: The volume below the threshold is used as a standard to
determine whether or not to hang up the phone.
Drop Silent Call Timeout: If the detected volume is below the threshold and the time
exceeds the silence detection interval, the gateway will hang up the phone automatically
to avoid keeping the line engaged.
NOTE: Please be careful with these settings. Improper values might cause unexpected automatic
disconnection of a call. Default values are recommended.
