ADC HDSL4 Manuale Utente

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 

. 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. 

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.

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.

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.

GND 5

B

B

A

BAT 8

7

H

10

Status

A

Frame GND J

RS-232

Network Management

A

1

Ring

Tip

9

K

Tip

Ring

HDSL4-L2

6

F

Tip

Ring

HDSL4-L1

RCV

System Alarm

B

2

Tip

Ring

LINE

LINE

XMT

BRG

BRG

MODE SEL(ACO)

Fuse

Alarm