A method of evaluating constraint functions, the evaluation being based at least in part on a control blade movement criteria. The electrical connector has a retainer to prevent detachment of the cam lever from the connector body during transit. The plurality of device units other than the first device unit receive the specific token packet to shift to and stay in a suspend state until the general token transmission time elapses, and then shift to a waiting state after the general token transmission time. In one embodiment, the flexible sleeve includes at least one corrugated portion to aid the desired flexibility.