16 August 06 FDM-FSK Preliminary User Guide
22
Dwg: A01230
Foldback Condition
Under
normal conditions
all the modems would have a static
display showing a two-ring operation.
With a failure of any Slave or a cable cut, the adjacent modems would fold back
to form a new ring, thus maintaining communications. Next a message is sent to
all the other modems in the system to flash their displays once a second to
indicate a ring fold-back has taken place. The above diagram shows a catastrophic
event at Slave 2, with the resulting graphics displays below.
R1
T1
T1
T1
T1
R1
R1
R1
FDM
Slave 1
FDM
Slave 3
DATA
See Ring Status
Displays Below
R2
R2
R2
T2
T2
T2
T2
R2
RING 1
RING 2
RTU /
Controller
RTU /
Controller
TMC
Computer
FDM
Master
RTU /
Controller
FDM
Slave 2
T1
R2
R1
T2
LOS
LOS
Normal
Fiber Status
T1
R2
R1
T2
LOS
LOS
Slave 3
T1
R2
R1
T2
LOS
LOS
T1
R2
R1
T2
LOS
FDM
Master
Slave 1
Fold-Back indication
Indicates “Fiber Communications”
are good in this segment.
Fold-Back indication
