Answer (Cbs Data Coupler) At Terminal; Both Ends; Multipoint Backup - IBM 3872 User Manual

Legend
LL= Leased line (dedicated channel)
SN = Switched network
IF= Interface
_ _ =Normal
____ =
SNBU
2020 Terminal with
Dual Communications Interface
Leased L
Program
ine
Network
--
LL
IF
t----1
SN
/
-
Switched
Program
- - - -
t---------
IF
1 - -
Program
2780 Terminal with
Dual Communications Interface
5406 or 5410
Terminal
LL
IF
i - - -
SN
IF
See note.
/
-
r - -
See note.
--
c:::3-;:::~=====
Dedicated Channel
3872
JI Modem
/
1-- - - -
--~
c3-:~=====
Switched Network
--
c::::3-:~=====
Dedicated Channel
-
3872
JI
Modem
/
t - - - - - -
__...
c:::3-~=====Switched
Network
~"-..
Dedicated Channel
. .
3872
Modem
s""'
Switched Network
--
Leased
Line~I
Sw;tched
Netwo~
-
====1---------i
Program - _ _ .....__ _ _ _.
L----
Note: Cable-switching is unnecessary if the 3872 is equipped with the
Fan-Out feature. The cable from the dual interface SN connector
is permanently connected to the receptacle for DTE #2
(Figure 3-6).
Figure C-4. Sample Terminal SNBU Configurations
Multipoint Backup
In addition to making planned cable or program changes,
using the 3872 Modem for SNBU operation requires
setting both 3872 Modems to 2400 SWITCHED or both
3872 Modems to 1200 SWITCHED. The polling list at the
CPU should be reduced to one terminal (or up to three
terminals if the Fan-Out feature is in use at the tributary
location), to avoid timeouts and interruptions; a delay
between polling or addressing cycles should be used to
reduce program interference.
Since unsolicited communications are not compatible
with multipoint programming, and since the multipoint
program must be used in an SNBU operation to provide
terminal addresses, automatic answering at the CPU is not
a valid configuration.
C-6 IBM 3872 Modem User's Guide
Manual Answering (CDT DAA) at Both Ends
Connecting and disconnecting in this configuration are the
same as for point-to-point backup. See "Point-to-Point Back-
up", previously discussed in this appendix.
Manual Answering (CDT DAA) at CPU and Automatic
Answer (CBS Data Coupler) at Terminal
Connecting and disconnecting in this configuration are the
same as for point-to-point backup. See "Point-to-Point
Backup".