A portion of a test head utilized to perform simultaneous automated at-speed testing of a plurality of devices that generate serial data signals having gigabit per second baud rates. According to preferred configurations, the magnetic field source includes a magnetic material layer extending over a side of the channel that is opposite a gate electrode of the transistor device. These two elements may be combined into one physical structure, or may be separate. The first and second dies are configured to be coupled to the substrate. Also a corresponding wavelength modulation spectroscopy apparatus, software, and method. At least one of cellular phones 102 measures congestion degree of surroundings by a congestion degree measurement unit 102B, transmits it to a main server 104 as congestion information, the main server 104 aggregates the congestion information from the cellular phones 102, stores it, and provides the congestion information relating to a specific location requested for the requester.