Media converter for converting 10BASE-T/100BASE-TX/1000BASE-T port to 1000BASE-SX/LX/ZX/SFP (MMF/SMF/single-core/dual-core) (LEX185X Series). Realizes an abundance of functions with DIP switches,and supports construction of a wide variety of optical networks. With improved product lifetime and high reliability, it can be designed for safe use. Optimum solutions are provided for construction of a wide variety of optical networks not only for companies but also for buildings, factories, dams, expressways, and railroads.