3Com Router 3000 Series Manual page 31

3Com Router Release Notes for V1.20
Table 22 lists the meaning of DIP switches for 4-port E1/CE1/PRI modules and
shows how to set them:
Table 22 DIP Switch Settings for the 4E1 Module
DIP
1BIT
2BIT
3BIT
4BIT
5BIT
6BIT
7BIT
8BIT
Caution:
To avoid damage to the interface module or router, verify that the identifier on
■
the interface is correct.
If the 4-port E1/CE1/PRI module is connected to a cable that extends outside
■
the building, you should install a lightning arrester at the input end of the cable
to for lightning protection.
To connect the interface cable to the 4-port E1/CE1/PRI module:
1 Power off the router.
2 Select the appropriate 4E1 cable and E1 cable according to the type of interface
on the remote device, and set the DIP switches of the 4-port E1/CE1/PRI module
correctly.
If the resistance of the interface in the remote device is 75-ohm, select the E1
■
75-ohm non-balanced coaxial cable and 75-ohm 4E1 conversion cable and set
all the DIP switches on the 4-port E1/CE1/PRI module to ON so the interface
resistance is 75-ohm.
If the resistance of the interface in the remote device is 120-ohm, select the E1
■
120-ohm balanced twisted pair cable and 120-ohm 4E1 conversion cable and
set all the DIP switches on the 4-port E1/CE1/PRI module to OFF so the
interface resistance is 120-ohm.
3 Plug the DB-25 connector of the 4E1 conversion cable into the DB-25 interface of
the 4-port E1/CE1/PRI module and secure the screws.
Configuration of 75-ohm
Meaning impedance
75-ohm/120-ohm ON
selection switch
ON
ON
ON
ON
RxRing grounding OFF: RxRing is grounded via
mode selection capacitance.
switch
ON: RxRing is grounded
directly.
RxShield -
grounding mode
selection switch
SxShield grounding -
mode selection
switch
31
Configuration of
120-ohm
impedance
OFF
OFF
OFF
OFF
OFF
-
ON: RxShield is
grounded.
OFF: RxShield is not
grounded.
OFF: RxShield is
grounded via
capacitance
ON: RxShield is
grounded directly.