20040001. The Exidor 3470 electro magnetic floor spring is ideal for use in hotel and hospital corridors, where doors need to be held in normal use. The hold open function can be linked to the building's fire alarm system to release and close the door when the alarm is activated, by cutting the power to the spring. The 3740 is supplied body only, complete with a cement box and is CE marked and Certifire approved.. Fixed power size 4. Suitable for doors up to 400kg. Highly efficient double cam mechanism. Unique 3° leading edge adjustment for improved alignment