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PRELIMINARY
XRT86VL38
REV. P1.0.6
OCTAL T1/E1/J1 FRAMER/LIU COMBO
394
When the E1 system runs normally, that is, when there is no Loss of Signal (LOS) or Loss of Frame (LOF)
detected in the line, no alarm will be generated. Sometimes, intermittent outburst of electrical noises on the line
might result in Bipolar Violation or bit errors in the incoming signals, but these errors in general will not trigger
the equipment to generate alarms. They will, depending on the system requirements, trigger the framer to
generate interrupts that would cause the local microprocessor to create performance reports of the line.
Now, consider a case in which the E1 line from the CO to the Repeater is broken or interrupted, resulting in
completely loss of incoming data or severely impaired signal quality. Upon detection of Loss of Signal (LOS) or
Loss of Frame (LOF) condition, the Repeater will generate an internal Red Alarm, also known as the Service
Alarm Indication. This alarm will normally trigger a microprocessor interrupt informing the user that an incoming
signal failure is happening.
When the Repeater is in the Red Alarm state, it will transmit the Yellow Alarm to the CO indicating the loss of
an incoming signal or loss of frame synchronization. This Yellow Alarm informs the CO that there is a problem
further down the line and its transmission is not being received at the Repeater. Figure 101 below illustrates
the scenario in which the E1 connection from the CO to the Repeater is broken.
F
IGURE
100. S
IMPLE
D
IAGRAM
OF
E1
SYSTEM
MODEL
E1 Receive
Framer Block
E1 Transmit
Framer Block
E1 Receive
Framer Block
E1 Transmit
Framer Block
E1
Transmit
Section
E1
Transmit
Section
E1
Receive
Section
E1
Receive
Section
CO
Repeater
CPE
Simple E1 System Model