Technical Reference for ZyXEL omni.net series

X.75 Outgoing Protocol

The X.75 protocol can be chosen using the following AT commands:

 

AT Command

 

Description

 

ATB00

 

X.75 with transparent layer 3.

 

 

 

 

 

ATB01

 

X.75 with T.70 NL.

 

 

 

 

 

 

The ATB0x commands not only specify the outgoing protocol, but also set the default layer 3 for an incoming X.75 call without layer 3 information. It is important for both ends of an X.75 connection to execute the same pre-assigned layer 3 protocol, as it reduces the chance that the ISDN TA will make the wrong protocol selection.

For European ISDN (DSS1), the Low-Layer-Compatibility (LLC) information element in the SETUP message can be used to specify the layer 3 protocol. Since this is an option for ISDN switches, some of the switches might not deliver the LLC information element to the remote end.

Table 46. X.75 Outgoing Protocol

Synchronous Connections (for omni.net LCD/LCD+M)

The ZyXEL omni.net LCD/LCD+M has synchronous mode included for transfering the data synchronously. Use the following commands to choose the data rate for synchronous operation:

 

AT Command

 

 

 

Data Rate

 

ATB11

 

 

 

64000bps

 

ATB19

 

 

 

56000bps

 

 

 

Table 47. AT Command for Synchronous Connections

 

There are two modes of synchronous operation:

Asynchronous commands, synchronous data (AT&M1): The omni.net LCD/LCD+M accepts

AT commands in asynchronous mode. Once the call is connected, it enters synchronous mode for data transmission.

Synchronous mode (AT&M3*I1): The omni.net LCD/LCD+M accepts synchronous commands from V.25 bis or a PC with an add-on synchronous card, and exchanges data synchronously with a remote TA. (For more information on Async to Sync conversion, please refer to Chater 7.)

8-5