ATL Telecom AM2048 - Manual (Page 28)

FIGURE 10.1 COPPER SYSTEM BLOCK DIAGRAM
10.1 COPPER TRANSMISSION
The copper system is intended for operation on 2-wire local telephone network circuits,
such as those meeting BT EPS-9 (Note: The AM2048 requires either one or two such circuits).
It will operate satisfactorily on unloaded lines having a wide range of characteristics; bridge
taps can be tolerated, dependent upon their characteristics. Although, the system requires a
base band circuit, a continuous loop at DC is not required. The system can transmit data at
user port rates between 64k and 2048k.
For the copper system, echo cancellation is used to eliminate the unwanted reflections of the
transmitted signal from the receiver input.
The line is connected to the transmission circuit via a line transformer, which acts as a balun
and provides isolation; there is surge protection across the transformer line connections.
The transmission circuit utilises a custom IC and a number of proprietary components to
perform the signal processing described above.
When more than one transmission line is in operation, each transmission system operates with
the same bit rate derived from an oscillator in the master unit.
Primary Rate
Interface
ATL
HDSL
Interface
Chip
DSP
Chip
Transceiver
Analogue
Interface
DSP
Chip
Transceiver
Analogue
Interface
Micro
Controller
Pair 1
Pair 2 G703
75/
120ohms
User Interface Module
Transmission Module
1 0 S Y S T E M O V E R V I E W
ATL TELECOM USER GUIDE
AM2048A
53
10
52 ATL TELECOM USER GUIDE
AM2048A
Example results for 0.4mm gauge cable, white gaussian noise:
Line will not train, but I know the ELU and NTU are connected.
If an ELU running in two pair mode is connected to an NTU running in one pair mode, the
transmission lines will never train.
Reprogram the ELU into one pair mode until synchronisation has been achieved and then set
the system back to two pair mode. Both units will then be in two pair mode and there will be
no problem. Warning: This will not work in the circumstance that the transmission line is too
long to allow training at the higher single pair data rate.
My internal BERT test doesn’t seem to work properly.
When running two AM2048 MKII's back to back in Structured G.703 mode using an internal
timing source and transparently passing TS0, an internal BERT will not work.
Temporarily generate TS0 at the NTU. The internal BERT will then work correctly.
How do I get back to the factory settings?
Go to the “Configuration>Software” menu.
Select the ‘Default Config.’ option.
Use the TAB key or the arrow keys to place the cursor in the box.
Press space bar to select the option.
Press ‘Enter’.
The unit will pause for a few seconds before re-booting.
The factory default for the desktop unit is an NTU.
For persistent problems please contact your local distributor for assistance.
ATL Transmission technical support is available by fax on +44 29 20 500 850 in the
first instance.
Line Length (km)
3.5
4.0
4.4
4.5
Error Rate
0
0
0
1xE-7
Noise Level
OFF
OFF
OFF
OFF
QF
450
860
1800
2300
S/N
31.9
29.1
25.8
55.0
Line Length (km)
2.75
2.75
2.75
2.75
Error Rate
0
0
1xE-7
1xE-6
Noise Level
OFF
0dBm
+0.5dBm
+0.9dBm
QF
280
5200
5500
5600
S/N
33.9
21.2
21.0
20.9