After a controller #1 delivers an interpolation command, a first operating means operates the length on an interpolation line in synchronism with a clock signal from a clock synchronization circuit (45). After a first step of forming a synthesized track frame (100) is executed based on the operated value, a transmitting means transmits the synthesized track frame (100) to a controller #2. After a second step of receiving the synthesized track operating frame is executed by a receiving means under control of the controller #2, the controllers #1,#2 control a second operating means to execute a third step of operating a position on the interpolation line based on the synthesized track frame (100).
