This product is an equipment that transmits bi-directional control data between the control keyboard and the receiver box over 1 core of optical cable.
It is a WDM (Wavelength Division Multiplexing) method that utilizes optical characteristics to transmit long-distance wirelessly and is not affected by electric and magnetic fields.
LEDs for data input and output indication are attached to the transmitting and receiving parts, so you can visually check the data communication status without separate equipment.