EM Locks

The Electromagnetic Lock (EM Lock) is the most commonly type of locks used with Card Access System. It is much cheaper and easier to install compared to other locksets. It can be used for glass doors, wooden door and even metal doors and gates. And with the correct mounting brackets, you can install on doors that swing out or swing in.

An electromagnetic lock is made up of two main parts: an armature plate made of a magnetic material and a metal plate surrounded by a coil of wire which can be magnetized. When current is passed through the coil, the metal plate becomes magnetized and strongly attracts the armature, locking the door.

The strength of an EM Lock is measured by the holding force in lbs. Typical range is 300 lbs, 600 lbs, 1200 lbs and 2400 lbs. A 300 lbs lock may be more suitable only for internal doors. Most doors uses a 600 lbs lock, including internal doors as the prices between a 300 lbs and a 600 lbs EM Lock is not significant. 1200 and 2400 lbs EM Lock are more typically used for metal doors and outdoor gates.

All EM Locks are "fail safe" meaning that in the event of a power failure, it will release the door. Therefore it is a common practice to connect the EM Lock to a power supply with a back up battery. The back up power will keep the lock energized for up to 4 hours.

From security perspective, it is better to mechanically lock the door after office hours even though you have an access system.  This is to ensure that even in a power failure situation, the door is still locked. 

Some people may question the usefulness of the card access system if you still have to depend on the physical mechanical lock.  The card access system ensures that only people who are authorised can enter and in the event of a networked system, the data of who enters and at what time will be stored for future investigation, provided there is power to keep it working.  The battery backup can sustain its operations for 4 hours and if needed, we can increase the battery backup capacity.  But if there is a sustained power failure or shutdown, and that time period exceeded the backup period, the door will still be left opened.  Hence it is good to lock the door mechanically particularly over the weekends or long holidays.

Alternatively, we should consider using other fail-secure locks such as the drop bolt and the electric latch.