Dual Redundancy
Dual redundancy refers to the idea that any part of a critical system can fail, and an equal replacement will automatically take over the intended operation. It is most commonly applied to deployment avionics to prevent lawn-darting.
An example of a proper dual-redundant deployment avionics system is as follows;
Each bay must contain 2 charges, in case the first was not enough to overcome the shear pins
Each of these charges must be connected to a separate deployment board, in case one of the boards fail
Each of these boards need to be connected to a separate battery, in case one of them fails