Northern UTA220/UTA220k manual Establishing an X.25 Virtual Connection, D-Channel

D-Channel X.25

Note: The AT@P1=P and AT@P1=D commands do not take effect until the TA power is cycled or the TA is restarted. The AT&W command must be executed to save all port parameters.

Establishing an X.25 Virtual Connection

There are three modes of operation for the PAD:

•Command mode

•Connect-in-progress mode

•Data transfer mode

Initially, the PAD is in the PAD command mode where PAD commands can be executed and an X.25 virtual connection can be established if the D-channel X.25 link is connected.

An X.25 virtual call can be established by initiating the PAD select command containing the desired requested facilities and/or Network User Address (NUA).

Refer to the PAD COMMAND SET section for the rules governing the format of the PAD select command. The facilities permit the user to request special services from the ISDN network at call-setup time. The NUA informs the ISDN packet handler of the remote location address the user is requesting for connection through the ISDN network.

Example: R-12345678

This command requests reverse charging and directs the virtual call to the NUA 12345678.

During establishment of the X.25 virtual call connection, the PAD is in the connect-in-progress mode. When the virtual call is established, the following message displays:

COM

The PAD is now in the data transfer mode and data exchange can begin.

Note: Data is transmitted through the PAD that is packeting the data. Echo of PAD data and PAD commands is performed locally by the PAD.

UTA220/UTA220k 12-3