
Customizing WAN Interfaces
114078 Rev. A 4-17
Enabling or Disabling Bipolar with 8-Zero Substitution
T1 uses bipolar format for signals. In bipolar format, alternating positive and
negative pulses on the digital line signify the number one, and the absence of a
pulse signifies zero.
A long string of zeros on a T1 line would cause the line to lose synchronization
due to lack of pulses. Bay Networks offers Bipolar with 8-Zero Substitution
(B8ZS) for T1 synchronization.
Refer to the “T1 Overview” section in Chapter 2 for detailed information.
You can enable or disable B8ZS support on this interface, depending on the ability
of the associated T1 equipment to support B8ZS.
Specifying the Physical Line Length
Line Buildout conditions the router signals to mitigate attenuation, and depends
on the physical length of the T1 line. You can configure a line length to a value
from 1 through 655 ft. By default, the T1 Line Buildout is based on a physical line
length of 1 foot.
You can configure the approximate length of the cable connecting the router and
the associated T1 equipment for this interface.
Setting the Internal Clock Mode
The T1 equipment associated with a T1 interface must use a compatible transmit
clock. The T1 interface supports three sources for the transmit clock:
• Internal -- Indicates that the router sets the clock.
• Slave -- Indicates that the incoming data stream sets the clock
• Manual -- Indicates that jumpers on the T1 link or net module set the clock.
You can set the Clock Mode on this interface.
Site Manager: B8ZS Support parameter: page A-71
Site Manager: Line Buildout parameter: page A-72
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