Interface Configuration Guide 7705 SAR Interfaces
Edition: 01 3HE 11011 AAAC TQZZA 133
In unidirectional mode, the K1 and K2 bytes are not used to coordinate switch action;
however, the K1 byte is still used to inform the other end of the local action, and bit
5 of the K2 byte is set to 0 to indicate 1+1 APS mode (see Table 17).
In bidirectional mode, the highest-priority local request is compared to the remote
request (received from the far-end node using an APS command), and whichever
request has the greater priority is selected. The requests can be automatically
initiated (such as Signal Failure or Signal Degrade), external (such as Lockout,
Forced Switch, Request Switch), or state requests (such as Revert-Time timers).
The channels requesting the switch action are assigned by bits 5 through 8. Only
channel number codes 0 and 1 are supported on the 7705 SAR. If channel 0 is
selected, the condition bits show the received protection channel status. If channel 1
is selected, the condition bits shows the received working channel status.
The K2 byte is used to indicate bridging actions performed at the line termination
equipment (LTE), the provisioned architecture, and mode of operation, as shown in
Table 17.
1100 SF - Low Priority
1011 SD - High Priority (not used in 1+1 APS)
1010 SD - Low Priority
1001 Not used
1000 Manual Switch
0111 Not used
0110 Wait-to-Restore
0101 Not used
0100 Exercise
0011 Not used
0010 Reverse Request
0001 Do Not Revert
0000 No Request
Table 16 K1 Byte Switch Priorities (Continued)
Bits Condition
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