Cisco 2600 Series Operation Manual page 90

1-Port and 2-Port Channelized E1/ISDN PRI Balanced (120-ohm) Network Modules
The CE1/PRI modules are available with one or two E1 ports and with balanced or
unbalanced interfaces. CE1/PRI modules receive and transmit data bidirectionally at the E1
rate of 2.048 Mbps and provide up to 30 virtual channels per E1 port. Each of the virtual
channels is presented to the system as a serial interface that can be configured individually.
The E1 interface is the physical media that supports ISDN PRI.
CE1/PRI Module Jumper Settings
Jumpers on the CE1/PRI modules can be used to connect or disconnect receive shield to
ground. (See Table 8-3.) The default setting for balanced, 120-ohm CE1/PRI-B modules
disconnects receive shield to ground. The default setting for unbalanced, 75-ohm
CE1/PRI-U modules connects receive shield to ground. If you are experiencing ground
loop problems with E1 cabling, you may want to try changing the jumper settings in the
module.
Table 8-3
CE1/PRI Module Type
Balanced, 120 ohm
Unbalanced, 75 ohm
Connecting CE1/PRI-B Modules to the Network
To connect a CE1/PRI-B (120-ohm) module to the network, use the appropriate cable to
connect the CE1/PRI-B port to an E1 CSU. (See Figure 8-13, Figure 8-14, and Figure 8-15,
showing DB-15, twinax, and RJ-45 CSUs respectively.)
8-10 Cisco Network Modules Hardware Installation Guide
CE1/PRI Module Jumpers
Default Jumper Setting Function
2 and 3
1 and 2
Disconnects receive shield from
ground
Connects receive shield to ground