Edwards Signaling 1504-AQN5 Electromagnetic door holder is a high quality device for use with single doors. The electromagnet assembly is designed for flush wall mounting. Designed to be used on self-closing, swinging doors to automatically isolate an area when activated by fire alarm, smoke detection or sprinkler systems. Can also be operated by manual control - wherever the instant closing of doors is necessitated for safety or for convenience. Hospitals - for stairwell doors, room doors, long corridors, schools - exit door (closes all doors at once by pushbutton control); offices (instant privacy by pushing a button on your desk), nursing homes and public buildings.