SCALANCE X accessory STP 991-1LD, pluggable for SCALANCE XM-400, 1x 100 Mbit/s ST/BFOC port, optical, single-mode glass up to max. 26 km. SCALANCESTP991-1LD pluggable transceivers offer the option of flexibly equipping modular Industrial Ethernet Layer 3 switches for optical connections. With an operating temperature range of -40 °C to +70 °C, the pluggable transceivers are particularly suitable for use in demanding environments. Cost savings thanks to the modular system. The structure of electrical and optical Industrial Ethernet networks as well as the network topology and port type can be easily adapted to the structure of the system and expanded at any time thanks to the modular system. End-to-end industrial network for data, voice and video.