A battery control module is provided for use with a battery and includes a voltage measuring module that measures battery voltage, a current measuring module that measures battery current, and a state of charge module that communicates with said current and voltage measuring modules. A locking cam on the frame on one side of said passageway has a line engaging portion, the cam being movable between a line releasing position and a line locking position. Eventually, the compact optical module permitting highly efficient optical coupling and having components thereof highly densely packaged can be provided. A circumferential position of the protrusion can also be altered, all in accordance with a quality that characterizes a machine state or vibration.