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Appendix B - Functional Operation LTPH-UM-1031-03, Issue 3
64 September 12, 2003 H4TU-C-319 List 1
APPENDIX B - FUNCTIONAL OPERATION
HDSL4 technology provides full-duplex services at standard T1 rates over two pairs of copper wire between an
H4TU-C, H4Ds (if necessary), and an H4TU-R which comprise one ADC system. ADC systems use Overlapped
Pulse Amplitude Modulation Transmission (OPAM) transceiver systems to establish two, full-duplex, 784 kbps
data channels between the H4TU-C-319 and a remotely located H4TU-R.
A block diagram of the H4TU-C-319 is shown in Figure 34. The H4TU-C-319 receives a 1.544 Mbps DSX-1 data
stream from the DSX-1 digital cross-connect interface. The H4TU-C-319 contains a DS1 frame synchronizer
controlled by an 8-bit microprocessor that determines the type of framing on the DS1 stream and synchronizes
with it. The H4TU-C-319 recognizes Superframe (SF), including D4, or Extended Superframe (ESF) framing.
When the data is unframed, the H4TU-C-319 arbitrarily defines a frame bit.
Figure 34. H4TU-C-319 List 1 Block Diagram
TIMING
The low-loop wander (0.5 UI max) of an H4TU-C, when used with remote units, allows the circuit to be used in
all critical timing applications, including those used to transport Stratum 1 timing.
GROUND FAULT DETECTION
The H4TU-C has a Ground Fault Detection (GFD) circuit which detects a ground or a resistive path to ground on
any wire of the HDSL4 loop. This makes the product compliant with the Class A2 requirements of GR-1089.
SPECTRUM ISSUES
The asymmetric 776 kbps spectrum, defined in ANSI T1.418 Issue 2, allows the HDSL4 product to be spectrally
compatible with ADSL services in adjacent pairs in the same binding groups for all non-doubler applications. A
combination of asymmetric and symmetric spectrums is used for ADSL compatibility in doubler applications.
HDSL
XCVR
Microprocessor
GND5
Power
Supply
Pre-equalizer
Select
B
B
A
BAT8
7
H
10
Status
A
FrameGND J
RS-232
NetworkManagement
A
1
Ring
Tip
HDSL
XCVR
9
K
Tip
Ring
HDSL4-L
2
6
F
Tip
Ring
HDSL4-L1
RCV
SystemAlarm
B
2
Tip
Ring
LINE
LINE
XMT
BRG
BRG
MUX
DEMUX
T1
Framer
MODESEL(ACO)
-185 Vdcor+/-123Vdc
PowerSupply
(GroundIsolated
andGroundFaultDetect)
DSX-1
D
SX-1
Fuse
Alarm