TRANSMISSION DEVICE, TRANSMISSION SYSTEM AND TRANSMISSION METHOD

摘要

PROBLEM TO BE SOLVED: To extend service life of a photo-coupler used for serial communication while maintaining appropriate data transmission.SOLUTION: A control unit 160 determines a current value of a primary side current of a photo-coupler 120 so that a current value of current flowing through a part where a transmitted device monitors will be within a predetermined current value range on a transmission path if secondary current is made to flow. A variable current circuit 150 supplies primary current with a current value determined by the control unit 160 to a light-emitting diode 121 included in the photo-coupler 120.