Section 150-431-114
Release 01
Page 4
3.04
The received HDSL channels are processed
by the transceiver and then passed on to the HLU-
431, List 1D demultiplexer module. The demultiplexer
provides frame synchronization for each of the two HDSL
loops. The demultiplexer and HDSL transceivers work
under control of the HLU-431, List 1D microprocessor and
compensate for data inversions caused by tip-ring reversals
and loop swaps caused by pair reversals. The HiGain
system allows for tip-ring or pair reversals, but does not
tolerate split pairs. By synchronizing to the Frame Sync
Word (FSW) of each loop, the demultiplexer can
reconstruct the original 1.544 Mbps DS1 stream from the
payloads of the two HDSL loops. The CRC fields on the
HDSL streams allow the HLU-431, List 1D to determine if
errors are present on the channel due to excessive
impairments on the HDSL pairs or excessive impulse or
crosstalk noise.
3.05
The demultiplexer removes data link messages
from the HDSL loops and passes them to the
microprocessor. This mechanism allows operations
messages and status to be exchanged between the HLU-
431, List 1D and the HRU-412 remote unit.
3.06
The reconstructed HDSL data is buffered in a
first-in-first-out (FIFO) buffer within the
demultiplexer. A frequency synthesizer, in conjunction
with the FIFO, regulates the output bit rate and
reconstructs the DSX-1 clock at the exact rate received
from the remote end. The HiGain system operates at T1
rates of 1.544 Mbps with up to
±
200 bps of offset.
3.07
A DSX-1 interface driver converts the input data
to an Alternate Mark Inversion (AMI) or Binary
Eight Zero Substitution (B8ZS) format. The DSX-1
equalizer is programmable to five different lengths, as
determined by the distance between the HLU-431, List 1D
and the DSX-1 interface. This provides CB-119
specification compliant pulses at the DSX-1 interface over
a range of 0 to 655 feet of ABAM-specification cable.
3.08.
The HLU-431, List 1D contains two separate
power converters. The main power supply
converts -48 Vdc local battery to logic power for the HLU-
431, List 1D circuits. The line power supply converts the
-48 Vdc battery to either 130 Vdc (for non-doubler
applications) or 200 Vdc (for doubler applications), then
provides simplex power feed on the two HDSL line
interfaces. Switch S2 allows the user to configure the
HDSL line powering voltage to be unipolar (0 to -130 V
and 0 to -200 V) or bipolar (
±
65 V and
±
100 V) (see
Figure 5.) The line power supply can be turned on or off
by the microprocessor and is automatically shut down in
the presence of line short circuits or microprocessor
failure.
3.09
A female 9-pin (DB-9) RS-232 connector is
provided on the front panel (see Figure 3). This
connector provides asynchronous access to the HiGain
system maintenance provisioning and performance
monitoring firmware. The port is configured as DCE with
8 data bits, 1 stop bit and no parity. Operator interaction
with the firmware is via an ASCII terminal or a Personal
Computer with asynchronous communication software.
Striking the Space bar several times enables the HLU-431,
List 1D to automatically match the terminal line baud rate,
from 1200 to 9600 baud. Figure 7 through Figure 14 show
the menu selections available from the terminal for non-
doubler applications. Figure 16 through Figure 34 show
the menu selections available from the terminal for
doubler applications. Table 8 defines the terms used in the
non-doubler System Status screen. Table 18 defines the
terms for the doubler System Status screens.
4. ALARMS
4.01
The normally open alarm contacts available
across pins 22 & 30 (Figure 4) comprise the
HLU-431, List 1D Minor Alarm output. These alarm
contacts close for any of the alarm conditions listed below.
Since more than one alarm condition can exist at any
given time, but only one message can be displayed, the
alarms are listed as follows in their order of priority. Only
the highest priority alarm is displayed if more than one
alarm condition exists. The ALRM message precedes
every specific alarm condition display.
1. ALRM LOSW: Either HDSL loop lost sync
2. ALRM LLOS: Loss of HLU DSX-1 input
signal
3. ALRM RLOS: Loss of HRU DSX-1 input
signal
4. ALRM TLOS: A user option that causes the
loss of the HRU DS1 input from the CI to
initiate a logic loopback in the HRU.
5. ALRM H1ES: HDSL loop 1 has exceeded
the 24-hour user-selected Errored Seconds
CRC threshold. If both H1ES and H2ES
occur, only H1ES is displayed on the front
panel.
6. ALRM H2ES: HDSL loop 2 has exceeded
the 24-hour user-selected Errored Seconds
CRC threshold. If both H1ES and H2ES
occur, only H1ES is displayed on the front
panel.
7. ALRM DS1: The total number of bipolar
violations (BPV), at either the HLU or the
HRU DS1 inputs, have exceeded the 24-hour
user-selected threshold.
