Black Box 5000 - Manual (Page 82)

Multiserver 5000
80
I NSTALL THE X.21 L INK
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 F EEDER M UX N ODE ID S
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 C HANNELS
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 C ALLS
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.