A child car seat includes a base and a backrest. The control circuit applies a first voltage to a selected one of a upper interconnections, applies a second voltage to an unselected one of the upper interconnections, applies a third voltage to a first dummy upper interconnection and independently controls the first to third voltages to be set to different values. Blades which are leading or lagging versus other blades will produce different timing signatures representative of alignment of the blades. A plurality of parallel slots is defined through both the inner plate and the left connection plate.