
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.