Interlocking availability depends on its power supply, so such facilities are designed with redundant supply from several independent sources: the public grid, the traction network and an emergency generator. Each input requires its own protection, and surge-protection selection depends on the network arrangement, voltage and frequency. For a public-grid supply in a TN-C 3~230/400 V, 50 Hz system, FLT-SEC-T1+T2-3C-350/25-FM is intended. Supply from the traction network in a TN-S 2~231/462 V system at 16.7 Hz is handled by FLT-SEC-P-T1-2S-350/25-FM-a variant selected specifically for railway-network parameters. For an emergency generator in TN-C-S and TT 3~230/400 V, 50 Hz systems, FLT-SEC-P-T1-3S-350/25-FM is specified.
FLT-SEC-P-T1-1C-440/35-FM performs a separate function: it connects the common potential of the CLIXTRAB module DIN rail to earth while maintaining system insulation during ground faults, allowing an isolated signalling installation to remain available.
All variants are combined Type 1+2 surge protective devices, carrying lightning impulse current from a direct strike while limiting surges to a level safe for equipment. The FM suffix in the catalogue designation indicates an integrated remote indication contact with a potential-free output, enabling protection status to be monitored without visiting the site. The product standards are EN 61643-11 and IEC 61643-11.
