A coupler for electrically connecting two coaxial cables together is disclosed. The control device 200 converts an image acquired by the camera 15 into coordinate information, calculates at least one representative point of the vehicle 1 and at least one target point situated on the trolley wire 3R, 3L based on the coordinate information, and executes the control to give a yaw moment to the vehicle 1 so that the representative point approaches the target point. The AGC system is designed to ensure a received signal power is at an optimal level for analog to digital conversion or any other form of signal processing.