7705 SAR Interfaces
138
Interface Configuration Guide
3HE 11011 AAAC TQZZA Edition: 01
3.2.15.7 APS Failure Codes
3.2.15.7.1 Protection Switching Byte Failure (APS-PSB)
This failure indicates that the received K1 byte is either invalid or inconsistent. An
invalid code defect occurs if the same K1 value is received for three consecutive
frames and is either an unused code or irrelevant for the specific switching operation.
An inconsistent code defect occurs when no 3 consecutive received K1 bytes of the
last 12 frames are the same.
If the failure persists for 2.5 s, a Protection Switching Byte alarm is raised. When this
failure is declared, the protection line is treated as if it were in the SF state. The
received signal is then selected from the working line.
When the failure is absent for 10 s, the alarm is cleared and the SF state of the
protection line is removed.
This alarm can only be raised by the active port operating in bidirectional mode.
3.2.15.7.2 Channel Mismatch Failure (APS-CM)
This failure indicates that there is a channel mismatch between the transmitted K1
bytes and the received K2 bytes. A defect is declared when the received K2 channel
number differs from the transmitted K1 channel number for more than 50 ms after 3
identical K1 bytes are sent. The monitoring for this condition is continuous, not just
when the transmitted value of K1 changes.
If the failure persists for 2.5 s, a Channel Mismatch Failure alarm is raised. When this
failure is declared, the protection line is treated as if it were in the SF state. The
received signal is then selected from the working line.
When the failure is absent for 10 s, the alarm is cleared and the SF state of the
protection line is removed.
This alarm can only be raised by the active port operating in bidirectional mode.
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