
150-388-105-05, Revision 05
Provisioning
HLU-388 List 5
March 25, 2000
25
Equalization Option
Equalization is the configuration of system transmission characteristics within specified limits. An adaptive
equalizer inserts a frequency-shaped loss that corresponds to an equivalent addition of an appropriate cable length.
By simulating the additional cable loss necessary for correct operation, the equalizer compensates for a range of
variation in transmission path characteristics.
BPVT Option
The HLU-388 List 5 improves HiGain’s compatibility with Digital Loop Carrier (DLC) feeder applications
because of its ability to transmit T1 BPV occurrences between its T1 interfaces. This feature is required to support
protection switching in DLC applications. Each DLC terminal must be able to monitor the integrity of its Receive
T1 payload and then switch to the protected line when the integrity of the path drops below specific user-selected
limits. An essential requirement of this feature is the need for each DLC terminal to detect BPVs in its T1 input.
Standard HDSL systems correct T1 BPVs at the input and thus prevent them from being detected by the DLC
terminals to which they are connected. The HLU-388 and its associated remote units remove this limitation and
become BPV transparent by detecting and counting input BPVs at each end, and then replicating them at the T1
output port of the distant end.
This BPVT option is controlled by the BPVT user option, which allows it to be Enabled (ENA) or Disabled (DIS).
In addition, the CRCs in each direction of every HDSL loop of each span are also counted and added in with the
BPV count to produce a Total Error Count (TEC) that indicates the integrity of both the T1 and HDSL paths. A
TEC in each direction is calculated each second by adding the number of BPVs to the number of HDSL CRCs in
that direction. The maximum TEC count is 12000. This TEC number is converted into BPVs at the distant end
during the following second at a rate of 1 BPV every 128 T1 bits up to a maximum of 12000 (BER=7.7 x 10
-3
).
This maximum rate is more than adequate since it exceeds the maximum 10
-3
BER required by most DLC systems.
When BPVT is enabled in systems with four or less doublers, the response time to an HDSL
LOSW is approximately 70 ms, which gives DLC terminals time to react and avoid dropped calls.