Black Box 5000 manual Link Configuration Description, See -2, X.21 Link

Multiserver 5000

INSTALL THE X.21 LINK

Assuming that you have installed and configured the modem for the X.21 link, connect the cable.

In X.21 link operation, the Multiserver must be connected to a feeder mux via an external modem. It cannot be connected to another Multiserver.

Appendix B: Cabling Diagrams has information on the cables you should use and their pin assignments.

X.21 FEEDER MUX NODE IDS

Renumber and rename the feeder mux after configuring the X.21 link. See Section 8.6, The Mux Link, for information on naming feeder muxes. The information that applies to muxes on feeder mux links also applies to muxes on X.21 links.

X.21 CHANNELS

There is no special async channel configuration required for use with X.21. However, there are special class and switching considerations. These are discussed in Section 10.11, X.21 Switching Considerations.

X.21 CALLS

An X.21 call is automatically initiated when:

	X.21 Link
Configuration		Description
1.	Data	Data activity is detected
	Activity	(and buffered in the calling
		unit until synchronization is
		established with the remote
		unit).
2.	DTR	DTR is transitions from low
		to high.

When the above occurs, the X.21 channel raises the DTR signal to the local line terminator. Once the call is established, the Multiserver and the attached feeder mux will synchronize. Data transmission will commence.

Should the Multiserver be unable to synchronize with the feeder mux, a LINK DOWN message is output and the port originating the call will display a DATA LOST message.

An X.21 link is automatically disconnected when:

	X.21 Link
Configuration		Description
1.	Data	No data activity for a time
	Activity	greater than configured on
		the No Data Activity Timer.
		(See Table 8-2, X.21 Link
		Parameters, option 3).
2.	DTR	DTR transitions from high
		to low.

To disconnect an X.21 link:

Press <break> three times within 5 seconds to disconnect an X.21 call.

80