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Configuring WAN Physical Links
• Timeslots (E1)
• Yellow Alarms (T1)
Cable length
Longer cable lengths cause greater losses for signals, so transmitter hardware must
transmit at a higher level to transmit data successfully. However, too high a signal level
can cause crosstalk from one cable to another. The cablelength parameter allows you to
control the transmitter signal level for your conditions. Typically, your service provider
will suggest the correct level.
The parameter values available differ for T1 and T3 links. For E1, the parameter value is
not changeable, but is always set to 120 Ohms. However, for E1 links you can configure
the receiver gain to meet your conditions. See the section Receiver Gain on page 2-5.
For short haul connections (less than 1000 feet) the typical equipment uses less sensitive
receivers. The transmitter level for T1 is set by selecting a cable length in feet, from the
following values: 133, 266, 399, 533 or 655. For T3, select from the following values: 249
or 900. Choose the next higher value if the cable length provided by your service
provider does not match one of these values. For example, choose 133 for a 50 foot cable
and 533 for a 450 foot cable. The default value is 133, which corresponds to cables in the
range of 0-133 feet.
For longer distances (up to 6000 feet) T1 equipment uses more sensitive receivers, and
crosstalk is more likely to occur. Under these conditions, the transmitter level is set by
selecting a transmitter attenuation level in dB from the following values: -22.5, -15, -7.5,
or 0.
From lowest to highest transmitter level, use the following values for the
config port
command: -22.5 db, -15 db, -7.5 db, 0 db, 133 feet, 266 feet, 399 feet,
t1 cablelength
533 feet, and 655 feet.
To configure the cable length, use one of the following commands:
config ports <portlist> t1 cablelength [0 | -7.5 | -15 | -22.5] db
config ports <portlist> t1 cablelength [133 | 266 | 399 | 533 | 655]
feet
config ports <portlist> t3 cablelength [249 | 900] feet
WAN Module Installation and User Guide
2-3
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