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Daniel is the Systems Engineer for a 130+ year old security integrator in Seattle. He holds a BS in Electronics Engineering Technology from Western Washington University.

Electrified Locks – A Solid Choice

In two prior posts, I have described the problems associated with two of the most common locking solutions for electronic access control, maglocks and electric strikes.  These are often perceived as being cheaper and easier to install, but, almost always, using electrified locks is a better decision.

Electrified locks are electronically controlled versions of the mechanical locks normally used to secure doors.  These can be cylindrical locks (key cylinder in the lever or knob), mortise locks (key cylinder above the lever), or exit devices (panic hardware commonly used on exterior doors and emergency exits).  Electrified locks are available to retrofit or substitute for every major brand of commercial lock.  Once installed, they look just like the mechanical versions, making for a cleaner, more professional appearance than maglocks or electric strikes.  Wires are connected to the doors through some type of power transfer, usually a normal looking hinge or pivot with wires concealed inside.

Electrified locks solve most of the problems involved in other locking solutions:

  • No visible modifications to door or frame.
  • Free egress is built in to the lock.
  • Deadlatch function is preserved for greater security.
  • Can always remain secure on the outside in most installations.

In summary, electrified locks typically provide more security, more safety, and better aesthetics than maglocks or electric strikes.

 

Electric Strikes – A So-So Solution

One of the most common choices for adding electronic control to door is the electric
strike.  Electric strikes are are attached to the frame of a door, replacing the mechanical strike that normally holds the latch of lock in the closed position.  They have a lip that swings outward, allowing the latch to clear the frame and the door to be opened. These avoid the major problems of maglocks, but bring a few downsides of their own.

Electric strikes come in a huge variety of designs and prices, with most commercial grade strikes costing from $150 to $500 dollars.  In general, the more you spend, the longer it will last.  Cheaper strikes may be appropriate for some doors, but higher end strikes will probably save money in the long run for heavily used doors.  There are strikes made to work with specific types of locks and frames and strikes made to work with the largest possible number of locks.  Some are designed to make installation easier.  Some are designed to be field-serviceable, allowing low cost refurbishing when parts wear out instead of replacement.

Electric strikes can be fail-safe (unlocked when power is removed) or fail-secure (locked when power is removed), and many are made to be convertible between this functions.  Electric strikes are typically paired with mechanical locks that are always locked from the outside and always unlocked from the inside.  These two features offer dramatic advantages over maglocks by allowing more careful control of which direction people can move in which situations.

On the other hand, electric strikes:

  • Require modification of the door frame.
  • Are subject to problems from changes in the way doors fit in their frames.
  • Sometimes compromise security.
  • Are of limited use on fire doors.

Require modification of the door frame.  Because of the way they work, electric strikes nearly always require that pieces of the door frame be cut out of the way.  When installed well, the strike fits the cuts well and the frame still looks okay.  But the electric strike can never be removed without leaving holes in the frame.  For this reason alone, some office buildings prohibit their use on tenant spaces.  The modification also increases the labor cost of installation.  Some strikes use clever designs that minimize or eliminate frame modification, but these are usually not suitable for high use doors.

Problems from changes in the way doors fit in their frames.  Even if an electric strike is installed perfectly, problems due to the fit of the door may occur down the road.  Many doors sag, settle, or warp over time, have small bumpers added to prevent slamming, or have air pressure differences between inside and outside.  All of these can cause the lock’s latch to press against the lip of the strike.  This, in turn, prevents the strike from unlocking, and the door appears to not work.  Some strikes allow a small amount of pressure, but this is limited.

Sometimes compromise security.  As explained in detail in this great article by Silva Consultants, poor alignment of an electric strike or changes in door fit (as above), especially on doors with cylindrical locks, can easily lead to the lock’s deadlatch no longer functioning.  The deadlatch is a secondary piece that extends from the edge of a lock, designed to prevent the most basic of bypass methods, opening the door with a plastic card.  If not properly aligned with the strike, the deadlatch is allowed to extend and offers no protection.  For this reason, doors with electric strikes are often protected by latch guards.  This does solve the problem, but a locking choice that requires an additional product to ensure security does not sound like a great idea to me.

Limited use on fire doors.  Fire doors are designed, and required by code, to prevent the spread of fire and smoke between certain areas of buildings.  To perform this critical function, fire doors must latch closed during a fire.  As electric strikes work by allowing the latch to move clear of the frame, they must be fail-secure AND must be tied into the fire alarm system to ensure they are secured in a fire.

Like maglocks, electric strikes are often used due to their familiarity.  Sometimes they cost less then better options, but sometimes they require less obvious expenditures that balance things out.

The Folly of Maglocks

Maglocks are large electromagnets attached to door frames, paired with metal plates affixed to the doors themselves, to electronically control when doors are locked and unlocked.  They are a common choice for electronically locking doors.  They are also the worst choice.

Most maglocks are well made products that do exactly what they are designed to do.  They solve problems that other locks cannot.  Sometimes they are the only way to electronically secure a door.  So, what is wrong with them?

Most of the problems stem from their nature as an electromagnetic device.  Though all electrified locks depend on electromagnetism, all other types can be classified as electromechanical.  They use electromagnetism (in the form of solenoids) to control the mechanics inside the locks, not to directly hold the doors closed.  Using electromagnetism to directly secure doors leads to a couple of serious problems:

  • Maglocks are always always unlocked when not powered.
  • Maglocks require additional devices to allow exiting.
  • Maglocks require additional devices for emergency entry.

Always unlocked when not powered.  In the security world, the term for this is fail-safe.  Sounds good – your doors should be safe, right?  Well, they should be safe for those inside and secure against those outside.  Choosing a maglock gets it wrong on both counts, because they leave your doors unlocked in an extended power outage (and often during a fire alarm – do you really want someone to be able to unlock your doors by pulling a fire alarm handle?) and. . .

Require additional devices to allow exiting.  Unlike electromechanical locks, maglocks have no inherent mechanical overrides.  To ensure people can safely exit in an emergency, maglock secured doors must (according to fire and building codes, as well as good practice) be equipped with motion sensors and emergency exit buttons, or panic-style push bars, all of which cause the maglock to release.  These add to the expense and complexity of the installation, and often create problems.  We frequently get complaints about this type of motion sensor either allowing anyone to get in by waving something through a gap in the door, or constantly unlocking the door due to people walking past the inside of the door.  This vulnerability is extremely widespread and has been used by penetration testers to get into all sorts of supposedly secure facilities.

Require additional devices for emergency entry.  Unless there is another door nearby that allows access to the same space with a mechanical key, a maglock secured door should be equipped with a keyswitch override on the outside.  In the event of a failure of the access control system, a mechanical key override is necessary to ensure emergency access by firefighters, building engineers, and security guards.  However, having the keyswitch adds another security vulnerability and adds to the installation cost.

So, why use them?  Architects like them because they are sometimes less obtrusive than other lock types.  Especially those of the subset known as shear locks, which are hidden from view when the door is closed, and even more problematic than standard maglocks.  Many people recommend them because they are not familiar with all the other options.  Some installers recommend them because they perceive them as being easier to install than other lock types.  Sometimes the cost is less, but people often forget to factor in the other components that maglocks necessitate.  None of these seem like strong arguments for choosing an inferior way to secure doors.

There are some circumstances where maglocks are the only solution.  A common one is on doors made entirely or almost entirely of glass (commonly referred to as Herculite doors).  I think that limitation, as well as a couple of other vulnerabilities, is a good reason not to use this type of door if security is important.  Most other circumstances that require maglocks are very specialized scenarios, and maglocks may be appropriate if the application is well thought out.

If maglocks are so problematic, what should be used instead?  Check back soon for articles containing the answers.

Introduction

After college, I learned that despite our need for more engineers, what the workplace really wants are engineers with at least two years of experience.  This frustration, paired with an introduction from a mutual friend, led to me taking a job as an apprentice installer with the electronic security division of Argens, Incorporated.  Though not the type of work I had envisioned in college, I was excited about this work because of a lifelong interest in security.  My senior project to earn my BS was, in fact, building and programming a Web based access control system (several years before Web based access control systems became popular).

My new employer had been in the locksmithing business since 1880.  As electronic access control became widely popular in the early 1990s, they had lots of work installing electrified hardware for the companies installing the control systems.  Realizing they already knew the most specialized part of the business, in 1994 they expanded into installing the controls themselves.  From there followed surveillance cameras and alarm systems.  By the time I was brought in, they had built a strong customer base that included large office buildings, federal agencies, and numerous private companies.

Thanks to my background in electronics and computers, and a quick grasp of new information, I worked my way up to leading new installation projects and getting tasked with most of the customer training and more complex software configuration.  I enjoyed the variety of places I worked, from pulling wire through the crawl spaces of historic buildings to focusing cameras in government evidence vaults.  I then moved into the office to do technical support, planning, and scheduling, and eventually settled into my current position of systems engineer.

Having worked in just about every aspect of designing, installing, and servicing electronic security systems, I have developed some opinions on good practices and products, and bad ones, that I decided it was time to share.