The redundancy manager ensures that at least X blocks of a group are on at all times. For example, if your ship has 5 antennas you can set it up so that (at least) 1 antenna is always on. So if an active antenna gets destroyed, a new antenna will be enabled within seconds.

Configuration is group based. Simply select all blocks that you would like managed and create a group named Redundant<whatever>

Using the antenna example, select all 5 antennas and create a group named RedundantAntenna (note that while <whatever> is "Antenna", it doesn't have to be -- it can be anything)

By default, the redundancy manager will ensure that at least 1 block in a group is always enabled.

You can change this by appending :<minimum number> to the group name.

Using the antenna example again, let's say we always want at least 2 antennas out of 5 enabled at all times: simply name the group RedundantAntenna:2

And that's it. The redundancy manager typically runs every 3 seconds.

Also remember that the redundancy manager only ensures that at least a certain number of redundant blocks are enabled. So if you have all 5 of the 5 antennas enabled (and it is configured to keep at least 1 active), the redundancy manager will not shut off 4 antennas. This is to keep things simple and is also a safety feature, since shutting off blocks would not be appropriate in all situations.