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Knowledge Base

The Interface Frequents UP&DOWN Because the Impedance of E1 Link of Router does not Match

Publication Date:  2012-07-27  |   Views:  109  |   Downloads:  0  |   Author:  Cao Jiping  |   Document ID:  EKB0000173391

Contents

Issue Description

When the E1 module of AR28-30 is connected with E1 cables of 120ohm, the interface frequents UP/DOWN.

Alarm Information

The alarm that the interface frequents UP/DOWN is prompted often. 

Handling Process

Draw the DIP switch BIT1~8 of the module to OFF, and the problem is solved.

Root Cause

1E1/2E1/4E1 modules have internal DIP switches, of which the setting determines the impedance of interface and the grounding. 
For the DIP switches of 1E1/2E1/4E1 modules, it is suggested to turn  BIT1~8 ON when they are connected with cables of 75 ohm, and OFF when with cables of 120 ohm. 
DIP of 1E1/2E1/4E1 modules is set to ON by default before shipment; that is, the impedance of E1 interface is 75 ohm. 

Suggestions

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