Methods and systems are provided for detecting a fuel system leak. A spring for movement balancing is connected to the upper arm at an intermediate position between the arm extremities hinged to the plates and is connected to the first plate at a point below the pivot point of the lower arm on the first plate. An bonding status inspection region, on which no metal film is formed, is formed in the crystal plate, and the bonding status inspection region is surrounded by or adjacent to the electrode pads. Each cooperative unit is configured to communicate the interface with the corresponding calling unit in response to a calling request received from the IP telephone terminal.