Siemens DataNET Hub (DNH) - Manual (Page 45)

2000585-001 Installation •••• 37
Signal Equalizer Settings for Non Recommended Cable or Unknown
Cable Lengths
This section is used to set the switches on the DataNET Signal Equalizer
Board. If:
• the type copper cable used for port connections is other than the
recommended cable
• the length of the cable runs are not known.
Read the section on the DataNET Hub Signal Equalizer Board (page 34)
as a prerequisite to this section.
When cable lengths are unknown, or the cable is other than the recom-
mended cable (Table 2-1), signal levels must be measured and com-
pared to determine the Signal Equalizer board settings.
Signals are compared by measuring the levels at each of the copper
ports and then adjusting the Equalizer board settings to within 3 dB of
the weakest signal.
If cable lengths are significantly different or if signals differ by greater
than ~4 dB, you may have to disconnect the cables on the short lengths
to activate the longer cables in order to make a measurement.
The DataNET HUB should bring up any single copper link independent
of the Equalizer board setting. Failure implies a connection problem or a
cable with excessive loss.
The smallest signal (longest cable) is used as the reference. This port
doesn not need a Signal Equalizer board. Attenuate all other siganl lev-
els greater than 3 dB (1.4 times larger) to a level within 3 dB of the
smallest signal. All signals should be within a range of 0.7 to 1.4 times
the amplitude of each other.
Use one of the two Connection Point options described on the following
pages to measure and evaluate the signal level of the slave device.
dB = 20 log (V(1)/V(2)); (6 dB is factor of 2 difference in amplitude)
V/1 = voltage measured for longest cable run
V/2 = voltage measured for switch setting port cable run
Description
Before You Begin
Cable Requirements
Signal Measurements
TIP
Comparing Signals
Example