Introduction
A door closer is defined as any mechanical device that closes a door in a controlled manner, preventing it from slamming, in general after someone opens it, or after it was automatically opened.
Feature
The force used to open the door is stored in some type of spring and when released this energy is then utilised to return the door to its original starting position (closed position). Many types of modern door closers can be linked to a buildings fire alarm system, in scenarios where doors need to be held open for the majority of the time they are held back with some sort of electro magnetic device, when the fire alarm is triggered it cuts power to the electro magnetic hold open device allowing the doors to close. These hold open devices can be separate to the door closer or part of its integral design.