A bridge comprises an interface to a plurality of hosts, an interface to a single-ported storage drive and arbitration logic. A plurality of channel units for controlling the data transfer to and from the central processing unit and a plurality of control units for controlling the data transfer to and from the magnetic disk drive are independently connected to the cache units and the nonvolatile memory units through data buses and access lines. Power measurement information based on transmissions occurring at irregular intervals may be combined in a beneficial manner to control transmission output power. Angular movement of the lever produces rotation of the magnet and is detected by the magnetic sensor which emits signals to a micro processor which, in turn, transmits such signals to external processing means.