3Com 5000 Series Installation Manual page 49

3Com Router 5000 Family
Installation Guide
Matching cable
Operating
mode
Function
2) E1 interface cable
E1 interface cable, which is G.703-compatible, may be 75Ω unbalanced coax cable or
120Ω balanced twisted pair cable.
75Ω unbalanced coax cable
The cable is attached with DB15 (male) connector for the router end, and with BNC
connector for the network end. See the following figure.
Figure 4-31 E1 75Ω unbalanced coax cable
Note:
You can also choose to attach both ends with BNC connectors, for extending two 75 
unbalanced coax cables.
120Ω balanced twisted pair cable
The cable is attached with DB15 (male) connector for the router end, and with RJ45
connector for the network end. See the following figure.
E1 75Ω unbalanced coax cable
E1 120Ω balanced coax cable
Coax connector, network interface connector, 75Ω−120Ω
converter (with BNC connector)
E1, CE1, ISDN PRI
Backup
Terminal access
ISDN PRI
3Com Corporation
4-22
Chapter 4 Installation of the Router