The invention provides a signal processing device. The signal processing device comprises a controller, as well as an optical fiber, an electric current loop and more than one first rigid line output interface, which are respectively connected with the controller. The controller parses the control information from the optical fiber and transmits the parsed control information to the subordinate equipment through the electric current loop, subpackages the parsed control information and then respectively transmits the subpackaged control information to the subordinate equipment through the corresponding first rigid line output interface, and packages brake state information from the electric current loop and then transmits the packaged brake state information to the higher equipment throughthe optical fiber. With the signal processing device provided by the invention, the subordinate equipment can be controlled by the control signal transmitted via the optical fiber.