An electrohydraulic control system that includes a plurality of electrohydraulic devices coupled to a remote master controller by a high-speed serial communication bus. The bus has a serial differential transmission line, and a control line for indicating impending transmission of data from one controller and conditioning the other controllers to receive information. Sections of the communication bus are electrically isolated from each other, while maintaining data and control line signal integrity therebetween, by electro-optical interface modules that include transmitters and receivers interconnected by lengths of fiber optic line, and interface drivers having signal ports respectively interconnecting the fiber optic transmitters and receivers to associated sections of the communication bus. An oscillator in the interface module at the isolated end of the bus cooperates with a filter in the module at the bus end of the optic fibers to condition the interface driver at the bus end to receive or transmit data from or to the bus as a function of the transmit/receive control output from the isolated controller. Interconnection is thus accomplished employing only a pair of fiber optic transmitters and receivers, and a pair of fiber optic lines, greatly reducing the cost that would otherwise be incurred if the transmit/receive control line were handled by separate fiber optics.