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. 

EM Locks Range

Electronic Drop Bolts

Electronic drop bolts are mortice electric locks that work differently from Electromagnetic Locks and overcome the two disadvantages of using Electromagnetic Locks. 

Electronic drop bolts can operate in either fail-safe or fail-secure modes.  Under the fail-safe mode, it will leave the door unlocked in the event of a power failure whereas under the fail-secure mode, it can keep the door locked when there is no power whereas the EM Lock will leave the door unlocked once there is no power.

With EM Locks, the door can only swing one way whereas with the electronic drop bolt, the door can swing both way.

The upper part of the bolt comprise the solenoid that drives the bolt and the lower portion comprise a door sensor with a guide hole.  For wooden door, the upper portion is installed into the door frame while a hole is bored into the top edge of the door to hold the bottom half.  When the door is closed, both upper and lower portion door sensors are aligned and the drop bolt is released into the guide hole, securing the door.  When a valid card is flashed at the reader, the card access controller will send a command to pull or retract the bolt, releasing the door.

Electronic drop bolt can be used for wooden doors, metal doors and glass doors.  For glass doors, suitable housing will be needed since the glass is too thin to embed the drop bolt. 

For the drop bolt to work properly, door alignment is crucial.  In many cases, the door alignment runs due to wear and tear, and the bolt is no longer in the dead center of the hole.  The bolt may have difficulty retracting or dropping, which may damage the solenoid coil. 

Electric Strikes

An electric strike replaces the fixed strike faceplate.  Like a fixed strike, it normally presents a ramped surface to the locking latch allowing the door to close and latch just like a fixed strike would. However, an electric strike's ramped surface can, upon command, pivot out of the way of the latch allowing the door to be pushed open (from the outside) without the latch being retracted (that is, without any operation of the knob) or while excited the knob or lever can be turned to allow egress from the secured area.

Electric strikes generally come in two basic configurations:

•  Fail-secure. Also called fail-locked or non-fail safe. The strike would remain locked in a power failure, but typically the knob can still be used to open the door from the inside for egress from the secure side.
• Fail-safe. Also called fail-open. Applying electric current to the strike will cause it to lock and if there is a power failure, the door would open merely by being pushed/pulled open.

Electric strikes are sometimes equipped with buzzers which allow someone outside the door to hear when the door is open. The buzzing noise is typically simply a result of applying AC current to the strike instead of DC, keep in mind the "buzzing" varies depending on voltage, and the coil or solenoid, although the buzzing from the AC current is audible, it is not designed to be loud for everyone to 'hear'. Using DC voltage, one would have to install an actual buzzer if they would want to "hear" the unit.

Electric Strikes Range