User guide

August 2001 83
Troubleshooting
Bipolar Violation In AMI line coding, ones alternate positive and negative
polarity, as described in Transmitting Digital Data on page 38.
A bipolar violation occurs when a one is the same polarity as the
preceding one.
Bipolar violations indicate that the application and the remote
end are not using the same line coding method, or the signal is
too weak for the board to detect it properly. Be sure the line
coding method your application uses is the same one used by the
carrier, as described in Configuring the Carrier on page 52. If
the line coding method is correct, then the signal might be too
weak for the board to detect it. Since the CO can handle weaker
signals, the CO might not experience bipolar violations. If the
board reports errors and the CO does not, a weak signal is
probably the cause.
Having a mismatch in the length of the CSU to board cable and
the equalization setting on the board can also lead to bipolar
violations. Check the equalization setting on the board as
described in your hardware installation guide to be sure they
are set for the correct length cable.
Sync The synchronization field indicates whether or not the network
and T1 board are synchronized. If they are not synchronized, it
means that the board is not receiving framing information. This
can happen if there is no signal on the line, if the board is
receiving an invalid or test signal (such as blue alarm), or if the
framing mode is not set properly. Be sure that you have set the
appropriate clock mode and framing method, as described in
Configuring the T1 Environment on page 47.
If changing the clock mode or framing method doesn’t restore
synchronization, the cable might be improperly installed or the
CSU is in loopback mode. Use a remote and a local loopback to
isolate whether the problem originates at the CO or your
system. For more information about loopbacks, see Configuring
the Loopback Mode on page 53 and Using Loopbacks on page 88.