US Patent 7457301 Vehicular communications system

In a case that a gateway unit connected with multiple networks receives mode managing data indicating an operating mode from a first network, the gateway unit sends mode managing data formed based on the received mode managing data only to control units and a gateway unit connected with a second network excluding the first network. This prevents both the gateways units from repeatedly exchanging mode managing data indicating a normal operating mode. Each control unit thereby rapidly transfers to a low power consumption mode when being able to operate in the low power consumption mode.