
CRS-300 1:10 Redundancy Switch Revision 16
Cables and Connections MN/CRS300.IOM
4–12
4.3 CDM-570/570L Modem Connections
If adding a modem to an operating 1:N system, care needs to be taken to not interfere with the
existing Traffic Modem. The cabling, power-up sequence must be correct to avoid contention in
the system from the modem Tx carrier. This sequence is detailed in
Chapter 7.4.5 (CONFIG)
ACTIVE MODEMS
.
MPORTANT
Traffic modems with differing data types can all be supported by the Redundant
Modem.
4.3.1 Control and Data Connections – CRS-300 to Modems
The 25-pin Control/Data Cable CA/WR0066 provides the EIA-422/232 traffic data path and
serial communication path between the Switch and the modems, and is therefore always required
even if the data type is G.703.
MPORTANT
Depending on the traffic data type, the appropriate jumper settings are provided
on the TMI to ensure proper operation for EIA-422
with RTS/CTS, DTR/DSR signal
using the CRS-320 (obsolete) or CRS-340 TMI. Refer to Chapter 4. MODEM, TMI,
AND SWITCH CONFIGURATION for this important configuration information.
Refer to Figure 4-6 to connect and secure the CA/WR0066 cables between each CDM-570/570L
and the CRS-300 as follows:
• DB-25M connector labeled “P1” on the RMI or TMI(s), to
• DB-25F connectors labeled “Data Interface” on the CDM-570/570Ls.
If G.703 is the traffic data type, also connect and secure the Data Cable CA/WR11999-6, used
for either Balanced or Unbalanced G.703 data, as follows:
• DB-15M connector labeled “P2” on the RMI or TMI(s), to
• DB-15F connectors labeled “Balanced E1/T1” on the CDM-570/570Ls.
4.3.2 User Data Connections – CRS-300 to User
The User’s traffic data from multiplexing equipment or a test data generator should connect to the
connectors labeled “User Data Interface” on the TMI(s). This interface replaces the direct
connection to the Traffic Modem’s “Data Interface” connectors.
MPORTANT
1. Because the Redundant Modem’s function is to replace a faulted
Traffic Modem, the RMI does not have a User Data Interface.
2. Ensure that the correct operation for Balanced or Unbalanced G.703
data is configured on the modem.
For T1/E1 operation, the optional CN-0000268 T1/E1 Adapter (illustrated in Figure A-32 in
Appendix A. CABLE DRAWINGS) may be purchased from Comtech EF Data to adapt the
Balanced G.703 DB-15F connector on the User data side of the TMI to a RJ-48 female connection.
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