In-train transmission control system and relay device

An in-train transmission control system in which first and second central units that are provided in any car of a train formation composed of one or more cars and control operation of the entire train formation transmit command data to a device or devices provided in some or all of the cars, and in which the device transmits device data to the first and second central units, comprising:

• first and second relay devices provided in the car and comprising network interfaces;
• and
• line concentrators connected between either one of the first and second central units and either one of the network interfaces of the first and second relay devices in the car, which allow the command data from the first and second central units to pass therethrough, and upon receiving device data from the device, transmit the device data to the first and second relay devices via the network interfaces,
• wherein the first and second relay devices aggregate the device data received from the line concentrators and transmit, via the network interfaces, the aggregated device data to the first and second central units.