Appendix C. External Channel Unit - Comtech EF Data SDM-309B Installation And Operation Manual

EXTERNAL CHANNEL UNIT
1.1 General
The following Appendix is an aide in interconnecting the SDM-309B modem with the
Multipoint M1200 channel unit for IBS service. The interface options are described in
Section 2. Figure C-1 is a block diagram of a satellite communications system using an
external channel unit with the SDM-309B modem.
1.2 System Integration
Connecting the channel unit to the modem as shown in this appendix will allow the
modem and channel unit to be automatically backed up in a M:N or 1:1 System. The use
of the special cables shown in this appendix is required to pass the fault lines to the
switch and to connect the DTE connectors of the channel unit to the DTE connectors of
the M:N or 1:1 switch.
The modem to channel unit interface options are:
RS422/449
V.35
The interconnect between the switch and the channel unit requires a special DTE to DCE
adapter cable to connect the two DTE connectors. The channel unit to switch interface
options are:
DS1/G.703
V.35
RS422/449
Note: Verify the switch settings in the M1200 are set for the proper interface selection.
The Alarm cable AS/0753 is used to sum the modem and channel unit alarms together
for fault reporting to the switch. The female molex connector (connector B) is to be
connected to the male molex connector on the cable between the switch and the channel
unit. Likewise, the male molex connector (connector C) is to be connected to the female
MN/U-SDM309B Rev. #
Use cable AS/0741 as the interconnect cable
Use cable AS/0479 as the interconnect cable
Use cable AS/0752 as the interconnect cable
Use cable AS/0750 as the interconnect cable
Use cable AS/0751 as the interconnect cable
Appendix C.
C-C–1