Black Box 5000 manual X.21 Link, Select option 5 on the Port Configuration Menu

8.7 The X.21 Link

INTRODUCTION TO X.21

Unlike the mux links (leased-line links), which are permanently connected, X.21 is a pay-as-you-go link. When a signal is raised, the network automatically establishes the link to the remote side. When you are finished, the link is dropped until it is again needed. The link is established on demand. X.21 is for data-only channels; it does not support voice or fax channels. In X.21 link operation, the Multiserver must be connected (via the PTT- provided line terminator) to a feeder mux (not another Multiserver).

This X.21 application (X.21 bis) is designed for Automatic Direct Call across an X.21 bis network. Automatic Direct Call means that any data or signal (DTR) activity on any Multiserver channel configured for X.21 applications causes the Multiserver to signal the network to initiate a call. Only one call route is required. Calls initiated locally and remotely (at the mux end) have the capacity to switch and contend for resources on the Multiserver.

PORT CONFIGURATION FOR THE X.21 LINK

Select option 5 on the Port Configuration Menu.

PORT CONFIGURATION [xxx]

5 X.21 LINK

A clocking message will not display; X.21 clocking is provided externally. You will be returned to the Configure Local Nodes Menu.

Important

The Multiserver must be node-reset (to current configuration) after the port has been configured for an X.21 link.

CHAPTER 8: Link Configuration

CONFIGURATION OF X.21 LINK PARAMETERS

After configuring the port for an X.21 link, the X.21 link parameters must be set. Select option 14 (X.21 Link Parameters) of the Configure Local Nodes Menu.

CONFIGURE LOCAL NODES [node id]

14 X.21 LINK PARAMETERS

ENTER NODE-ID/CHANNEL # (^X TO ABORT):

You will be prompted:

If the port is not configured as X.21, you will receive an error message:

** NOT X.21 LINK **

Most likely, a node reset was not done after the port was configured for the X.21 link. Do a node reset and access this menu again.

The X.21 Link Parameters Menu then appears (see next page). Each of the menu options is discussed in detail in Table 8-2.

After the X.21 Link Parameters are configured, perform a link reset. (See Section 11.1, Reset, and Table 11-1, Reset Options, for further information.)

After resetting, the Multiserver will exchange information with the feeder mux and, approximately 20 seconds later, the link will drop until an X.21 call is initiated.

The CCM indicator lights do not reflect the X.21 link status. The Command Facility Node Status display will show the link status (see Section 8.8, Review Link Configuration).

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