PURPOSE: To make the positioning of a receiver easy, by using infrared ray for signal transmission and using guide light as visual light for positioning for reception side.

CONSTITUTION: A transmission signal from an infrared ray diode 2 is transmitted as parallel lumonous flux 4 via a concave mirror 3 from a transmission side 1 to a reception side 5. A visual light diode 9 provided at a position shifted by (e) from the center of the luminous flux 4 transmits a visual light 8 to the reception side in parallel with the luminous flux 4. The center of the spot light of the visual light 8 is obtained at the reception side 5, the amount of eccentricity (e) is actually measured and the position of a convex mirror 6 on a fitting stand 10 is determined so that the center of the luminous flux 4 becomes the center of the convex mirror 6 as an antenna. Thus, the transmission signal with the luminous flux 4 can be converged into a photodetector 7.