ADC HDSL4 Appendix B Functional Operation, Timing, Ground Fault Detection, Spectrum Issues

Appendix B - Functional Operation LTPH-UM-1031-03, Issue 3

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.

Ablock 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.

Tip	A
DSX-1	XMT
Ring	1
BRG
LINE

Fuse	10	A
Alarm

BAT 8
B	Power
	Supply
GND 5

Network Management 7

T1

Framer

MUX

DEMUX

A

B

HDSL

XCVR

-185 Vdc or +/-123Vdc

Power Supply

(Ground Isolated

and Ground Fault Detect)

Tip

F

HDSL4-L1

6

Ring

Frame GND J

System Alarm H

LINE

BRG

Tip B

DSX-1 RCV

Ring 2

Pre-equalizer

Select

MODE SEL(ACO)

Microprocessor

Status RS-232

HDSL

XCVR

Tip

K

HDSL4-L2

9

Ring

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.

64 September 12, 2003 H4TU-C-319 List 1