Introduction
33
Model 3088A/I User Manual
4 • Operation
Test modes
The 3088A/I offers test modes in the form of loopbacks, PRBS pattern generators, and combinations of both.
This section discusses how the test modes work.
Figure 8
is a block diagram of the Model 3088A/I with respect to test modes.
Figure 8. Model 3088A/I Block Diagram
Loopbacks
The 3088A/I supports both Local Analog Loopbacks (LAL) and Remote Digital Loopbacks (RDL). These can
be initiated by the console command dsl set loopback <off|lal|rdl>. The data path for the LAL is shown in
figure 9
.
Note
Local loopback causes bit errors on the remote end if the link is up.
.
Figure 9. Local Analog Loopback diagram
The data received is looped back before going out on the DSL line. Note that this loopback occurs after the
pattern generator/BER meter. This means that running a 511 pattern in conjunction with an LAL should
result in no error detected by the meter.
The data path for the RDL is shown in
figure 10
.
Figure 10. Remote Digital Loopback diagram
The RDL causes the remote unit to loop the data received from the DSL line back tow the DSL line.
DSL
Framer
511 Pattern
Generator
511 BER
Meter
DSL
Framer
511 Pattern
Generator
511 BER
Meter
Line
DSL
Framer
511 Pattern
Generator
511 BER
Meter
DSL
Framer
511 Pattern
Generator
511 BER
Meter
Line
DSL
Framer
511 Pattern
Generator
511 BER
Meter
DSL
Framer
511 Pattern
Generator
511 BER
Meter
Line
