AudioCodes Mediant 2000 User Manual page 508

Parameter
Web: Detect Fax on Answer
Tone
EMS: Enables Detection of
FAX on Answer Tone
[DetFaxOnAnswerTone]
[T38FaxSessionImmediate
Start]
SIP User's Manual
and the parameter IsFaxUsed to 1, 2, or 3.

The "FAX" prefix in routing and manipulation tables is case-
sensitive.
Determines when the device initiates a T.38 session for fax
transmission.

[0] Initiate T.38 on Preamble = The device to which the called fax is
connected initiates a T.38 session on receiving Preamble signal
from the fax (default).

[1] Initiate T.38 on CED = The device to which the called fax is
connected initiates a T.38 session on receiving a CED answer tone
from the fax. This option can only be used to relay fax signals, as
the device sends T.38 Re-INVITE on detection of any fax/modem
Answer tone (2100 Hz, amplitude modulated 2100 Hz, or 2100 Hz
with phase reversals). The modem signal fails when using T.38 for
fax relay.
Notes:

For this parameter to take effect, a device reset is required.

This parameters is applicable only if the parameter IsFaxUsed is
set to 1 (T.38 Relay) or 3 (Fax Fallback).
Enables fax transmission of T.38 "no-signal" packets to the terminating
fax machine.

[0] Disable (default)

[1] Enable
This is used for transmission from fax machines (connected to the
device) located inside a Network Address Translation (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.
508
Description
Document #: LTRT-68814
Mediant 2000