Vehicles equipped with air brake systems and onboard vehicle management computers may be programmed to determine normal operating variables for the air compressor system used for maintaining air brake system pressure. In accordance with certain implementations, user software selectively specifies a list of network interfaces or addresses on which connections are to be accepted. Each node outputs a gamma voltage. The rotor has a spacer and a plurality of bearings, with each bearing at least partially confined between the spacer and the lining.