AudioCodes Mediant 1000B - Page 194

User's Manual 194 Document #: LTRT-27055
Mediant 1000B Gateway & E-SBC
 Enables echo cancellation for fax
 Disables echo cancellation for modem
 Performs certain jitter buffering optimizations
The network packets generated and received during the bypass period are regular voice
RTP packets (per the selected bypass coder), but with a different RTP payload type
according to the following parameters:
 'Fax Bypass Payload Type' (FaxBypassPayloadType)
 ModemBypassPayloadType (ini file)
During the bypass period, the coder uses the packing factor, configured by the 'Fax/Modem
Bypass Packing Factor' parameter (FaxModemBypassM). The packing factor determines
the number of coder payloads (each the size of
FaxModemBypassBasicRTPPacketInterval) that are used to generate a single fax/modem
bypass packet. When fax/modem transmission ends, the reverse switching, from bypass
coder to regular voice coder is performed.
 To configure fax / modem bypass mode:
1. Open the Gateway General Settings page (Setup menu > Signaling & Media tab >
Gateway folder > Gateway General Settings), and then from the 'Fax Signaling
Method' drop-down list (IsFaxUsed), select No Fax.
2. On the Fax/Modem/CID Settings page, do the following:
a. Set the 'Fax Transport Mode' parameter to Bypass (FaxTransportMode = 2).
b. Set the 'V.21 Modem Transport Type' parameter to Enable Bypass
(V21ModemTransportType = 2).
c. Set the 'V.22 Modem Transport Type' parameter to Enable Bypass
(V22ModemTransportType = 2).
d. Set the 'V.23 Modem Transport Type' parameter to Enable Bypass
(V23ModemTransportType = 2).
e. Set the 'V.32 Modem Transport Type' parameter to Enable Bypass
(V32ModemTransportType = 2).
f. Set the 'V.34 Modem Transport Type' parameter to Enable Bypass
(V34ModemTransportType = 2).
3. Set the ini file parameter, BellModemTransportType to 2 (Bypass).
4. Configure the following optional parameters:
• 'Fax/Modem Bypass Coder Type' (FaxModemBypassCoderType).
• 'Fax Bypass Payload Type' (FaxBypassPayloadType).
• ModemBypassPayloadType (ini file).
• FaxModemBypassBasicRTPPacketInterval (ini file).
• FaxModemBypasDJBufMinDelay (ini file).
Note: When the device is configured for modem bypass and T.38 fax, V.21 low-
speed modems are not supported and fail as a result.