Wednesday 18 July 2012

AIS-CI and RAI-CI Generation and Detection

The device can transmit and detect the RAI-CI and AIS-CI codes in T1 mode. These
codes are compatible with and do not interfere with the standard RAI (Yellow) and
AIS (Blue) alarms. These codes are defined in ANSI T1.403.


The AIS-CI code (alarm indication signal-customer installation) is the same for both
ESF and D4 operation. Setting the TAIS-CI bit in the TR.T1CCR1 register and the
TBL bit in the TR.T1TCR1 register causes the device to transmit the AIS-CI code.
The RAIS-CI status bit in the TR.SR4 register indicates the reception of an AIS-CI signal.

The RAI-CI (remote alarm indication-customer installation) code for T1 ESF operation
is a special form of the ESF Yellow Alarm (an unscheduled message). Setting the RAIS
-CI bit in the TR.T1CCR1 register causes the device to transmit the RAI-CI code. The
RAI-CI code causes a standard Yellow Alarm to be detected by the receiver. When
the host processor detects a Yellow Alarm, it can then test the alarm for the RAI-CI
state by checking the BOC detector for the RAI-CI flag. That flag is a 011111 code in
the 6-bit BOC message.

The RAI-CI code for T1 D4 operation is a 10001011 flag in all 24 time slots. To
transmit the RAI-CI code the host sets all 24 channels to idle with a 10001011 idle
code. Since this code meets the requirements for a standard T1 D4 Yellow Alarm, the
host can use the receive channel monitor function to detect the 100001011 code
whenever a standard Yellow Alarm is detected.

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