A pull station is an attached device on the fire system that is mounted on a wall surface near strategic locations that initiates a fire condition when pulled by a person in the building. In essence, it is triggered when a user pulls the handle down and completes the electrical circuit that locks the handle thus sounding the alarm siren. A fire system has either a single action or double action pull station.
Single Action Pull Station
When a single action pull station is activated, it must be manually restored back to its original position before the fire system can be reset to normal status. For extra protection, it must be restored to the ready position using a special pull station reset key designed just for this purpose. A single action pull station is self explanatory has it just takes a single action to trigger an alarm response. One of the disadvantages to this type is that you can set it off by just brushing up against it. To combat this problem, a pull station with a glass covering would require the operator to break the glass pane to release an internal spring triggering the system.
Double Action Pull Station
With advances in technology and changes in the national fire alarm code, it is now required that a double action pull station be installed versus the single action. This type needs a two hand motion such as lift up and pull down. Some operate on a push in and pull down mechanism. Nevertheless, all new fire alarm installation require the newer double action pull station.