User guide

82 RealCT Direct API Developer Guide
Chapter 3: T1 Networking
Yellow The CO sends a yellow alarm to indicate that it is not receiving
a valid signal from your system. If the T1 board receives a
yellow alarm, then the connection from the remote end to the
local end is good, and the problem is in the data transmitted to
the remote end from the local end.
One reason for a yellow alarm is faulty wiring. The connection
uses one pair of wires to transmit data and one pair to receive
data. A yellow alarm could happen if the wire pair that
transmits data from the board to the CO is broken or
disconnected but the other wire is in good condition. To see if the
wiring is faulty, set the board in a remote loopback where all
data transmitted by the CO is immediately transmitted back to
the CO by the board. If all the wiring is good, the CO receives
the same data it generates, and the alarm it generates should
disappear. In this case, the problem is probably that the board
is sending faulty data.
If the CO continues generating a yellow alarm in a remote
loopback, the wire could be faulty anywhere from the board to
the CO. To identify if the problem is with the network lines or
with the customer premise lines, use a CSU loopback. In this
mode, all data transmitted by the CO is immediately
transmitted back to the CO by the CSU. If the problem
disappears, the faulty line lies between the CO and the T1
board. If the problem does not disappear, the problem is with
the network lines.
Blue A blue alarm is a signal containing all ones. If the framing bits
are also ones, then the blue alarm is an unframed all ones. If the
framing bit follows the appropriate pattern then the signal is a
framed all ones.
Either end can send a blue alarm to test the data link. You can
also send a blue alarm to test a trunk that cannot send calls. In
either direction, when the blue alarm is removed, the alarm
should clear and synchronization should be restored. If the
alarm clears but the ends are still not synchronized, then your
application and the CO are probably using a different framing
method. See Configuring the Carrier on page 52 for more
information on how to set the correct framing method.
Slips Buffer slips indicate that the T1 board is not reading and
writing data to the line at the same rate as the remote end.
Usually, an incorrect clock setting or faulty clock source is
responsible for buffer slips. For more information about setting
the clock, see Setting the Clock on page 47.