DLS DLS 400A, Operating Manual

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Appendix D
Page 201
Appendix D NOISE GENERATOR CONNECTIONS
The theory behind connecting up the impairments generator to the wireline is simple, but
sometimes leads to confusion. When testing access equipment, the tests generally consist
of:
1) A pair of modems, the equipment under test.
2) A wireline or wireline simulator, over which the modems communicate
3) One, or sometimes two, impairments (noise) generators, which impair the trans-
mission conditions on the wireline, and make it more difficult for the modems to
train up and communicate.
4) A pair of error rate testers (test sets), which send data to and receive data from the
modems. These may also perform call set up and termination, and always have
some method of determining the quality of the received data. In many cases, they
are Consultronics Lynx testers.
This is shown here, diagrammatically, assuming one noise generator is used:
Simulators such as the Consultronics DLS 400(E), DLS 200 and DLS 100A can all con-
tain both the wireline simulation and the noise generator, and is the equipment enclosed in
the dotted lines. You do not have to worry about connecting wireline simulator and noise
generator together because this is already done inside the unit.
External to the unit, you must connect up the modems using a balanced interface. This bal-
anced line is shown diagrammatically, both inside and outside the unit by the
lines.
You just connect up using twisted pair wire—or better, screened twisted pair—from the
modems to the DLS unit. It is best to keep the connecting wire short, since then it picks up
N o ise
G en
Test
S e t
M od em
D L S U n it
M od em
W ire lin e
Test
S e t