A rocker switch unit with fuse comprising a housing ; a rocker switch lodged pivotally in the housing ; at least a fuse lodged in the housing and at least two connection elements for connecting the rocker switch unit with an external apparatus, wherein the two connection elements are connected to each other by the fuse, when rocker switch is in an ON-position. A state machine operates according to plural shift states to control each scan path in capturing data from response outputs of the combinational logic and then shifting one bit at a time to reduce the capacitive and constant state power consumed by shifting the scan paths. The key exchange is terminated if the first timeout expires and the key exchange is incomplete.