How To Defeat an ElectroMagnetic Traction Lock (Maglock) Jackson Research

How To Defeat an ElectroMagnetic Traction Lock (Maglocks)

Magnetic Traction Locks (maglocks) as constructed for the electronic security market are usually built from EI transformer lamination core. The high grade versions use silicon steel laminations, not stamped sheet metal as is commonly found in Asia. These devices are fundamentally classical traction electro-magnets. The force between the stator and the armature (strike plate) varies with Grade according to the following table. The holding force or Grade for any particular lock can easily be estimated based solely upon size. All 1200 pound holding force locks are roughly the same size.

BHMA/ANSI Grades	Locking Strength	Applications
Grade 1	1500 - 2700 lbs.	High Security
Grade 2	1000 - 1400 lbs.	Medium Security
Grade 3	500 - 900 lbs.	Light Security Traffic Control

The figure below shows a maglock cross-section with the EI lamination in gray, the coil in orange and a spacer plate in blue. In normal operation, there is no spacer plate. The strike plate and the coil lamination (stator) are in direct contact for maximum force. Insertion of any non-magnetic material will diminish that force based upon the separation introduced, x.

The graph below is characteristic of a 1200 pound holding force magnet and may vary depending upon construction technques. The curve as shown is not meant to be applicable data, but only an example. Any lock to be defeated should be tested with an adequate spacer for optimum performance. It is clear to see that the holding force diminishes rapidly with very thin non-magnetic material spacers. It has been observed that a tree leaf blown into the space between the stator and the armature while the door was closing reduced the maglock holding force by 50%.

This is a typical vendor's maglock with a holding force of 1200 pounds. An 0.015 inch aluminum sheet cut to fit the strike plate and fixed by an adhesive will go unnoticed and reduce the magnet locks holding force from 1200 pounds to approximately 300 pounds. Most men can put that much shoulder into jarring the device open. The door will appear firmly latched and secure with a holding force of 300 pounds, but actually will be lightly latched and insecure. This technique requires very careful inspection with the door open to spot and will probably go unnoticed by guards casual inspection. It is nearly impossible to detect by visual inspection with the door closed.

Any non-magnetic material can be used to defeat a maglock, such as clear plastic, provided it is easy to over look. Clearly, red electricians tape might not go unnoticed for very long. Aluminum tape of the type used for EMI shielding would also work quite well provided adequate thickness is achieved. Some maglocks check to see if there is electrical contact between the transformer laminations of the stator and the metal strike plate. Non-magnetic metal sheets and metal EMI tape are therefore the preferred methods. The objective is stealth. How would you know if the maglock below has been compromised?

Jackson Research has a proprietary IntelligentMagnetics™ method of determining if the maglock has been compromised.