AudioCodes Mediant 500L User Manual page 1116

Parameter
CED Transfer Mode
configure voip > media fax-modem > ced-
transfer-mode
[CEDTransferMode]
T.38 Fax Session
configure voip > sip-definition settings > t38-sess-
imm-strt
[T38FaxSessionImmediateStart]
V.150.1 Modem over IP
Note: These parameters are applicable only to the Gateway application.
Profile Number
[V1501AllocationProfile]
User's Manual
Mediant 500L Gateway & E-SBC
Description
IsFaxUsed parameter is set to 1 (T.38 Relay) or 3
(Fax Fallback).
Defines the method for sending fax/modem CED
(answering) tones.

[0] Fax Relay or VBD = (Default) The device
transfers the CED tone in Relay mode and
starts the fax session immediately.

[1] Voice Mode or VBD = The device transfers
the CED tone in either Voice or Bypass mode
and starts the fax session on V21 preamble.

[2] RFC 4733 Blocking RTP VBD = The
device transfers the CED tone in RFC 2833.
This is applicable only to V.150.1 modem
relay and fax bypass.

[3] RFC 4733 Along with RTP VBD = The
device transfers the CED tone in RFC 2833
and bypass, in parallel. For combined V.150.1
modem relay and fax relay, use this option.
Note: The parameter is applicable only to the
Gateway application.
Enables fax transmission of T.38 "no-signal"
packets to the terminating fax machine.

[0] Disable (default)

[1] Immediate Start on Fax = Device activates
T.38 fax relay upon receipt of a re-INVITE with
T.38 only in the SDP.

[2] Immediate Start on Fax & Voice = Device
activates T.38 fax relay upon receipt of a re-
INVITE with T.38 and audio media in the SDP.
The parameter is used for transmission from fax
machines connected to the device and located
inside a NAT. Generally, the firewall blocks T.38
(and other) packets received from the WAN,
unless the device behind NAT sends at least one
IP packet from the LAN to the WAN through the
firewall. If the firewall blocks T.38 packets sent
from the termination IP fax, the fax fails.
To overcome this, the device sends No-Op ("no-
signal") packets to open a pinhole in the NAT for
the answering fax machine. The originating fax
does not wait for an answer, but immediately
starts sending T.38 packets to the terminating fax
machine.
Note: To enable No-Op packet transmission, use
the NoOpEnable and NoOpInterval parameters.
Defines the V.150.1 profile, which determines
how many DSP channels support V.150.1.
The value range is 0 to 20. The default is 0.
Note: For the parameter to take effect, a device
1116 Document #: LTRT-10532