ATL User Guide
AM200 Modem
133
14
14 SYSTEM OVERVIEW
14.1 COPPER TRANSMISSION
Figure 71 System Block Diagram
The copper system is intended for operation on 2-wire local telephone network circuits, such as those meeting
BT EPS-9. 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 baseband circuit, a
continuous loop at DC is not required. The system can transmit data at user port rates between 64k and 2.3M
on a single pair.
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.
14.2 DSL TRANSMISSION FRAME
The transmission system operates in a bit pump mode. The DSL frame is sent over this 'data pipe'. The DSL
frame contains the following
· Sync word
· Stuff bits
· Stuff control bits
· EOC channel
· Customer data
