T.38 Fax Settings (H.323)
T.38 Fax Transmission
The options below are applied to the outgoing faxes:
Check this option if you want to have a possibility to use Error Correction Mode (ECM) for outgouing T.38 faxes. The ECM value can be overridden by the Outgoing Call Routing settings.
Select maximum bitrate for outgouing T.38 faxes. Maximum bitrate value can be set 14400/9600/4800 which corresponds to rate limits of standard protocols used for facsimile. The Maximum bitrate value can be overridden by the Outgoing Call Routing settings.
This option provides a forced switching to T.38 mode immediately (0 seconds) or after the specified time interval (1-20 seconds). Fax Voip FSP sends T.38 re-invite to the other side without waiting for T.38 re-invite or CED tone from the other side. By default, Fax Voip FSP switches to T.38 if only T.38 re-invite is received from the other side. This option can be overridden by the Outgoing Call Routing settings.
This option provides a forced switching to T.38 mode if the fax machine specific tone (CED signal) is detected. Fax Voip FSP sends T.38 re-invite to the other side without waiting for T.38 re-invite from the other side. By default, Fax Voip FSP switches to T.38 if only T.38 re-invite is received from the other side. This option can be overridden by the Outgoing Call Routing settings.
T.38 Fax Reception
The options below are applied to the incoming faxes:
Check this option if you want to have a possibility to use Error Correction Mode (ECM) for incoming T.38 faxes. The ECM value can be overridden by the Incoming Call Routing settings.
Select maximum bitrate for incoming T.38 faxes. Maximum bitrate value can be set 14400/9600/4800 which corresponds to rate limits of standard protocols used for facsimile. The Maximum bitrate value can be overridden by the Incoming Call Routing settings.
This option provides a forced switching to T.38 mode immediately (0 seconds) or after the specified time interval (1-20 seconds). Fax Voip FSP sends T.38 re-invite to the other side without waiting for T.38 re-invite or CNG tone from the other side. By default, Fax Voip FSP switches to T.38 immediately after answering an incoming call (0 seconds). This option can be overridden by the Incoming Call Routing settings.
This option provides a forced switching to T.38 mode if the fax machine specific tone (CNG signal) is detected. Fax Voip FSP sends T.38 re-invite to the other side without waiting for T.38 re-invite from the other side. This option can be overridden by the Incoming Call Routing settings.
T.38 UDPTL Redundancy
T.38 provides facilities to eliminate the effects of packet loss through data redundancy. When a packet is sent, either zero, one, two, three, or even more of the previously sent packets are repeated. (The specification does not impose a limit.) This increases the network bandwidth required (it’s still much less than not using T.38) but it allows the receiving gateway to reconstruct the complete packet sequence, even with a fairly high level of packet loss. The T.38 redundancy number corresponds to how many previous packet payloads are repeated with each packet. The values for (I)ndication, (L)ow (S)peed and (H)igh (S)peed IFP packets are specified separately.
Indication
Specifies the number of redundant T.38 fax packets to be sent to indicate CNG, CED tones, no signal. Ranges varies from 0 (no redundancy) to 5.
LS-Redundancy
Specifies the number of redundant T.38 fax packets to be sent for the low-speed V.21-based T.30 fax machine protocol. Low speed is used during the fax negotiation phase which is done at 300 Bps and is most likely to be affected by bad QoS. Ranges varies from 0 (no redundancy) to 5.
HS-Redundancy
Specifies the number of redundant T.38 fax packets to be sent for high-speed V.17, V.27, and V.29 T.4 or T.6 fax machine image data. High speed is used during the transmission phase which is done between 2400 Kbps and 14400 Kbps. Although bad QoS will deteriorate image quality, a few missing scan lines ultimately does not effect the human's perception of the received image. Ranges varies from 0 (no redundancy) to 5.
The T.38 redundancy values for (I)ndication, (L)ow (S)peed and (H)igh (S)peed IFP packets can be overridden by the Outgoing Call Routing and Incoming Call Routing settings.
Notes