The UIM-2E1 can be configured to use Cyclic Redundancy Check (CRC) to detect line errors and
scrutinize data integrity across the E1 line by appending, to the end of each E1 frame being
transmitted, a hexidecimal checksum calculated from the contents of the previously transmitted E1
frame. Remote E1 equipment makes a similar calculation upon receipt of each E1 frame and then
compares it to the checksum of the following E1 frame.
1.2.2 Line Code
Line code is the E1 mode of transmission. The two line code options outlined below fall within the
International Telecommunication Union - Telecommunication Standardization Sector (ITU-T) G.703
Standards for Transmission Facilities.
1.2.2.1 High Density Binary 3
High Density Binary 3 (HDB3) is used to accommodate the minimum ones density requirement
in the European public network. HDB3 line encoding helps prevent loss of synchronization
between the UIM-2E1 and remote E1 equipment by using bipolar violations to guarantee the
presence of pulses in the E1 line.
1.2.2.2 Alternate Mark Inversion
Alternate Mark Inversion (AMI) simply alternates positive and negative pulses. Although AMI
links typically encounter long strings of zeros which can potentially cause loss of
synchronization between units, Net to Net Technologies' products meet the European
minimum ones density requirement internally such that, even with AMI, loss of synchronization
is prevented between the UIM-2E1 and remote E1 equipment (just as it is with B8ZS).
1.3 Install the UIM-2E1
1.3.1 IP DSLAM Installation
The UIM-2E1 provides an upstream network connection, via a multiplexer uplink
module (MUM), for
Net to Net Technologies' IP DSLAMs; neither an IP DSLAM nor a MUM can function without an uplink
interface module (UIM).
1.3.1.1 Affix the UIM-2E1 to a MUM
z
Select a port on the MUM for installation of the UIM-2E1: either port (1 or 2) may be
used. Although not required for operational purposes, if redundancy is desired two UIMs
may be installed on a MUM, one in each port.
Switch #3 Frame Type
down
Cyclic Redundancy Check
up
No Cyclic Redundancy Check
Switch #4 Line Code
down
High Density Binary 3
up
Alternate Mark Inversion
N
OTE
The UIM-2E1 can be installed on a MUM that is already in service, though you must remove the MUM
from the IP DSLAM chassis in order to do so.
Removal of a MUM from a powered IP DSLAM will
not affect the operational status of other modules within the chassis; it will however,
disengage the IP DSLAM's upstream network connection.
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