Answering An X.75 Call; Making An X.75 Call - ZyXEL Communications ACCESSING INTERNET & INTRANET omni series User Manual

Answering an X.75 call

There is no need to configure the ISDN mode to the protocol of an
incoming call. The omni will be able to determine the correct
protocol to use by examining the data coming in from the remote site
if the device is set to auto-answer or once an answering command is
issued.
One exception to this is when the ISDN data call is carried through
Speech bearer. In this case, you would need to make an MSN entry
for the phone number from which you are expecting the Data-over-
Speech-bearer call. Use AT&ZI0=n. Refer to the section entitled
"Data over Speech Channel" in Chapter 5 for details.
To allow the TA to answer the incoming call, you need to set S0 to a
value greater than 0 (ie. ATS0=1). The TA will answer the call and
use asynchronous to synchronous conversions to and from the DTE.
If S0 is not set (S0=0), the DCE will report "RING" to your terminal.
External models will also make an audible ring notification.

Making an X.75 Call

CAPI 1.1a specifies X.75 with T.70 NL as its default.
CAPI 2.0 specifies X.75 with transparent layer 3 as its default.
The default data protocol of the TA is ATB20 (V.120). X.75
protocols can be chosen using the following AT commands:
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 TA will make the wrong protocol selection.
66 X.75 ISDN Communications