3Com MSR 50, MSR 30, MSR 20 manual 120-ohm, DIP switch Description Ohm impedance Impedance

SIC-1EPRI/SIC-1E1-F 29

Table 5 Interface attributes of SIC-1EPRI/SIC-1E1-F

Attribute	Description
Operating mode	E1
	CE1, ISDN PRI (supported by SIC-1EPRI
	only)
	FE1(supported by SIC-1E1-F only)
Supported service	Backup
	Terminal access
	ISDN (supported by SIC-1EPRI only)

DIP Switch E1/CE1/PRI interface is compatible with both 75-ohm impedance and 120-ohm impedance. The interface matches different types of impedance through an 8BIT DIP switch. By default, all the 8 positions of the DIP switch are ON, as shown in the following figure:

Figure 18 Default setting of the DIP switches

on

1

2

3

4

5

6

7

8

8BIT description and settings of DIP switch are given in the following table:

Table 6 Description and settings of the internal DIP switch of SIC-ERRI/SIC-1E1-F

			120-ohm
DIP switch	Description	75-ohm impedance	impedance
1BIT	Switch for	ON	OFF
	75-ohm/120-ohm
2BIT		ON	OFF
	options
3BIT		ON	OFF
4BIT		ON	OFF
5BIT		ON	OFF
6BIT	Switch for RxRing	OFF: RxRing grounding	-
	grounding mode	via capacitor
	options	ON: RxRing directly
		grounding