R2511-HP MSR Router Series Voice Configuration Guide(V5)

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Signals that a G3 fax machine receives and sends are modulated analog signals. Therefore the router
processes fax signals in a different way than it processes telephone signals. The router needs to perform
A/D or D/A conversion for fax signals (that is, the router demodulates analog signals from PSTN into
digital signals, or modulates digital signals from the IP network into analog signals), but does not need
to compress fax signals.
A real-time fax process consists of five phases:
1. Fax call setup phase. This phase is similar to the process of a telephone call setup. The difference
is that the fax tones identifying the sending/receiving terminals are included.
2. Prior-messaging phase. During this phase, fax faculty negotiation and training are performed.
3. Messaging phase. During this phase, fax packets are transmitted in accordance with the T.4
procedure, and packet transmission is controlled (including packets synchronization, error
detection and correction, and line monitoring).
4. Post-messaging phase. During this phase, control operations such as packet authentication,
messaging completion, and multi-page continuous transmission are performed.
5. Fax call release phase. During this phase, the fax call is released.
FoIP configuration task list
Before configuring FoIP, configure POTS and VoIP voice entities. For more information about the
configuration procedure, see "Configuring voice entities."
After VoIP configuration, you can make IP phone calls. Usually, the default FoIP configuration can be
used to send and receive faxes so long as a fax machine is connected. FoIP configuration is mainly to set
the specific FoIP parameters, or used for some particular situations where the fax cannot be made by
using the default transmit energy level of a gateway carrier.
Task Remarks
Configuring fax interworking protocol Required.
Enabling CNG fax switchover Optional.
Enabling ECM for fax Optional.
Configuring fax faculty transmission mode Optional.
Configuring maximum fax rate Optional.
Configuring fax training mode Optional.
Configuring threshold of local training Optional.
Configuring transmit energy level of gateway carrier Optional.
Configuring T.38 faculty description compatibility Optional.
Configuring global default parameters for fax Optional.
Configuring fax interworking protocol
The device supports two fax protocols: T.38 protocol and standard T.38 protocol. The standard T.38
protocol should be selected for interworking with leading fax terminals in the industry. Since most
leading fax terminals in the industry do not support the local training mode, the end-to-end training
mode must be selected for interworking with them.