Answer / rohit kumar

A redundant controller is a pair of standard controllers
on separate 2-wide power/controller carriers that are
connected together. Each controller
requires its own power supply mounted on its carrier. One
of the controllers in the pair is the active controller and
the other controller is the standby controller. There is
no physical difference between the active and
standby, nor is there a preferred position for the active
controller. The controller that boots first becomes the
active controller.
The redundant controllers communicate with each other via a
dedicated high-speed serial bus
The standby controller contains the same configuration as
the active controller and tracks the operation of the
active controller. When an active controller fails, the
standby controller takes over, providing uninterrupted
control
operation without initialization or user intervention. When
the previously active controller recovers to a healthy
state or is replaced, the two controllers automatically
become a redundant pair again.When the active controller
failed the user will recieve an alarm at the HIS

Answer / janani murugesan

As my point of view , here we have two controllers, one is working controller, another one is standby controller. the standby controller is called as the redundant controller. the redundant controller also have a capacity like working controller. actually here we feed the logic to DCS for when the working controller will be failure, the standby controller automatically will be started. so here we put standby controller into auto mode in DCS. so when the working controller is trip or any cable damage or other failure, the redundant (standby) controller is automatically in line.

Answer / asha

Actually there will be no difference between an active
controller & a standby controller both will be performing
the same actions, but there will be an alarm poped up as
soon as any one controller fails in this case the faulty
controller becomes the standby. And once it recovers from
the fault the active controller copies all the records
which it had accumulated during the fault meanwhile the
controller will be having a led glowing at the standby
contoller at the COPY indication once the standby
controller comes in line with the active controller it
indicates HARDRDY. In this way the redundant controller
operates fault.

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