150-231-175-01, Revision 01
Appendix C - Functional Operation
HLU-231 List 7E
September 23, 1998
49
A
PPENDIX
C - F
UNCTIONAL
O
PERATION
PairGain HDSL technology provides full-duplex services at standard T1 rates over copper wires between an HLU
and an HRU, which comprise one HiGain system. HiGain systems use PairGain 2-Binary 1, Quartenary (2B1Q)
HDSL transceiver systems to establish two, full-duplex, 784 kbps data channels between the HLU-231 and a
remotely located HDU or HRU. This provides a total capacity of 1.568 Mbps between the two units.
A block diagram of the HLU-231 is shown in
. The HLU-231 receives a 1.544 Mbps DSX-1 data stream
from the DSX-1 digital cross connect interface. The HLU-231 contains a DS1 frame synchronizer controlled by
an 8-bit microprocessor that determines the type of framing on the DS1 stream and synchronizes to it. The
HLU-231 recognizes Super Frame (SF), including D4, or Extended Super Frame (ESF) framing. When the data
is unframed, the HLU-231 arbitrarily defines a frame bit.
Figure 23.
HLU-231 Block Diagram
HDSL 2
XCVR
HDSL 1
XCVR
MICROPROCESSOR
POWER
SUPPLY
B
A
B
27
35
26
34
TIP
TIP 1
RING
RING 1
HDSL 2
HDSL 1
-48V39
15
19
44
16
GND
32
STATUS
A
RS-232
42
43
TIP
RING
D
S
X
1
RCV
49
50
20
21
TIP 1
RING 1
ALRM
SPAN
SPAN
XMT
D
S
X
1
BRG
BRG
MUX
DEMUX
PRE-
EQUALIZER
SELECT
T1
FRAMER
MODE SEL
FUSE
ALARM
-140V or ±100V HDSL LINE
VOLTAGE POWER SUPPLY
(GROUND ISOLATED)
