Surface holding magnet 828, Surface holding magnets are suitable for locking doors electromagnetically. They are easy to install. No changes or cutouts need to be made to the door frames. According to a letter dated March 24, 1991 from the Institute for Construction Technology, Berlin, electromagnets can also be attached to fire doors. A contact for the locking signal (Hall sensor) is integrated in the electro surface holding magnet 828. The magnet has a sturdy aluminum housing and is available in natural color and dark bronze anodized., With counter plate, with Hall sensor, 12/24 V DC, holding force 5000 N, aluminum color anodized, The nominal voltage can be set to 24 V DC or 12 V DC on the magnet., Please note when ordering: In addition to the integrated locking signal, an additional door contact is required.