
Configuring Line Services
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Editing E1 Lines
This section describes how to edit the line parameters for E1 link modules:
• Enabling or Disabling an E1 Line
• Enabling or Disabling CRC Checking
• Enabling or Disabling High-Density Bipolar Coding
• Setting the Clock Source
• Assigning Channel Functions
Enabling or Disabling an E1 Line
By default, the router enables E1 line services when you add the interface. You
can disable or reenable this interface without moving physical cabling.
Enabling or Disabling CRC Checking
Some E1 equipment expects a 4-byte Cyclic Redundancy Check (CRC) trailer at
the end of each frame. You can configure this interface to add the CRC trailer to
received frames by enabling it as a a CRC Line Type.
By default, the CRC trailer is not added to received E1 frames. Set CRC Checking
to E1CRC4 if the E1 equipment expects a 4-byte CRC trailer at the end of each
frame.
Enabling or Disabling High-Density Bipolar Coding
E1 uses bipolar format for signals. In bipolar format, alternating positive and
negative pulses on the digital line signify the number one, and the absence of a
pulse signifies zero. A negative pulse must always follow a positive pulse, and
vice versa. High-Density Bipolar Coding (HDB3S) is a mechanism to maintain
sufficient 1s density within the E1 data stream. Refer to the “Bipolar Format” in
Chapter 2 for more information.
Site Manager: Enable parameter: page A-27
Site Manager: Line Type parameter: page A-28
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