Appendix C Setting the fixed E1 port
impedance
CAUTION:
The DIP switches are located at the mother board inside the router chassis. To operate the DIP switches,
you must open the router chassis. For more information, see the chapter “Installing and upgrading internal
modules.”
By default, the impedance of the fixed E1 port on MSR20-12/20-12-W is 75 ohms. By using the internal
DIP switches, you can change the interface impedance from 75 ohms to 120 ohms.
Figure 52
Default setting of DIP switches
on
1
2
3
4
5
6
7
8
Table 1
DIP switch setting description
DIP Description
Configuration of
75-ohm impedance
Configuration of
120-ohm impedance
1BIT
75-ohm/120-ohm
selection switch
ON OFF
2BIT ON
OFF
3BIT ON
OFF
4BIT ON
OFF
5BIT ON
OFF
6BIT
RxRing grounding mode
selection switch
OFF: RxRing is grounded
via capacitance.
ON: RxRing is grounded
directly.
N/A
49
