3Com VCX v7111 User Manual page 178

Parameter
Fax/Modem Bypass Coder Type
[FaxModemBypassCoderType]
Fax/Modem Bypass Packing
Factor
[FaxModemBypassM]
CNG Detector Mode
[CNGDetectorMode]
Configuring the RTP / RTCP Settings
To configure the RTP / RTCP Settings parameters:
Open the RTP / RTCP Settings screen (Advanced Configuration menu > Media Settings
1
> RTP / RTCP Settings option); the RTP / RTCP Settings screen is displayed.
178
Description
Coder the gateway uses when performing fax/modem bypass. Usually,
high-bit-rate coders such as G.711 should be used.
You can select:
G.711 A-law 64 [0] (default).
G.711 μ-law [1] .
Number of (20 msec) coder payloads that are used to generate a
fax/modem bypass packet.
The valid range is 1, 2 or 3 coder payloads.
The default value is 1 coder payload.
[0] = Disable (default). Do not detect CNG.
[1] = Relay. CNG is detected on the originating side. CNG packets are
sent to the remote side according to T.38 (if IsFaxUsed=1) and the fax
session is started.
[2] = Events Only. CNG is detected on the originating side. The CNG
signal passes transparently to the remote side and fax session is started.
Usually T.38 fax session starts when the 'preamble' signal is detected by
the answering side. Some SIP gateways don't support the detection of
this fax signal on the answering side, thus, for these cases it is possible to
configure the gateways to start the T.38 fax session when the CNG tone
is detected by the originating side. However, this mode is not
recommended.
3Com
®
VCX V7111 VoIP Gateway User Guide