STP T2 40 is the series of Type 2/Class II devices for discharging
voltage surges, in accordance with EN/IEC 61643-11 and certified UL
1449 4th Ed. Suitable for the second stage of protection in supply
distribution panels in which Type 1 protection devices are installed
upstream, or for the first stage of protection in commercial or other
applications not exposed to direct strikes and with no external
lightning protection system.