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Cabinet Access Control

Rutherford Controls 3510 Electric Cabinet Lock

Cabinet security was already a concern in hospitals where drug theft is a problem, but has become an increased concern particularly in U.S. hospitals where new HIPAA privacy security regulations have mandated that patient data be secured by key or pass code locking device.  There are a wide variety of locking arrangements available to accomplish the task.

Simplex combination cabinet locks appear often in this application.  They are relatively inexpensive, not too hard to install, and accomplish basic compliance with HIPAA.  The regulations state that access to codes (or keys) should be limited, however, when you have a five-button mechanical combination lock, several hundred people can know the combination in a very short time by word of mouth.  Therefore a more costly and complex solution might be necessary in order to comply with the spirit of the regulations that are designed to actually protect patients’ privacy.

The best way to control people is to make them individually responsible.  That’s what electronic access control is all about.  Typically an institution adopts electronic access control for the audit trail capabilities that monitor who does what, where and when.  So if a patient’s information goes viral on the ‘Net, the debacle can more probably be traced back to its source.

As for credentials, biometrics is the most secure since one cannot share their fingerprint, but card or fob credentials are also effective.  People are less likely to share any credential that can be traced back to them.  Of course, unlike a fingerprint on a live finger, a card or prox fob could be stolen.   I do recommend a physical credential of some kind because PIN numbers are too easily shared.

The drawback to electronic security as applied to cabinets is that most available, good access control hardware tends to be hard wired.  Wiring can be difficult in such tight spaces, yet there are some solutions available.  For example, a resourceful access control installer could use an SDC model 1583 electromagnetic cabinet lock and an IEI Prox.pad keypad/proximity reader to secure a cabinet.  For a fail secure locking device, an RCI 3513 electric cabinet lock could be substituted for the SDC 1583.  The system would run on 24 volts DC and would need a power supply, but at least you could get audit trail and time zone capability out of it, with a Wiegand output for your existing access control system.

There are some glimmers of hope.  There are some stand-alone, battery operated cabinet locks that read a proximity card or i-Button.  But these are simply add-and-delete-user systems that allow control of who has access but does not keep track of when.  Without audit trail capability, access control is little better than that Simplex mechanical combination lock or a regular cabinet lock with its regular brass key.

For now the ultimate solution for cabinet security seems to be to put the cabinet in a locked room and use access control on the room rather than the cabinet.  But I think that will change, don’t you?

Multi-function Doorways, Part Two

Secured stairwell doors are among the most basic multi-function door applications.  In most jurisdictions they must (usually)* be both unlocked and positively latched in the event of a fire.  Unlocked so that if a person, fleeing into the stairwell during a fire, finds the stairwell full of smoke, they can safely exit the stairwell.  Positively latched so that the door will remain latched closed against the spread of the fire.

Until there is a need for access control, a passage function mortise lock, cylindrical lock with UL listed latch or exit device with passage function trim are fine.  The application begins to get interesting when the need arises to lock a stairwell door.

Right up front, electric strikes are out of the question because of the unlocked/positive latching requirement mentioned above.   It is not possible to positively latch a door when the electric strike is unlocked.  There is no such thing as a fire rated, fail safe electric strike.  If you configure a fire rated electric strike to be fail safe it voids the fire rating.

Since electric strikes are unusable for this application, that leaves either electric locks or electromagnetic locks.  Both have advantages and disadvantages.  Fail safe electric locks positively latch whereas mag locks allow the installer to us the existing hardware on the door to accomplish positive latching.  Electric locks require running wire through the door and some means of getting the wire from the frame into the door, such as an electric through-wire hinge.  Not all inspectors like electromagnetic locks, so before you install them be sure to check with your local Authority Having Jurisdiction (AHJ ) – that is, Fire Marshal or Building Inspector.

If the stairwell door already has a fire rated exit device installed, there is probably a fail safe electrified trim available for it.  Once again, this means an electric through-wire hinge or other power transfer device would be required.  Sometimes existing exit devices are incompatible with the electrified trims available for that brand and model of device.  If that is the case, the exit device might have to be replaced with one that is compatible with electrified trim.

Alternatively, there are after market request to exit (a.k.a. RX) switches available for most exit devices.  One could be used to release an electromagnetic lock on the stairwell door.

Usually it is required that all electric locking devices on stairwell doors be controlled by the fire alarm panel.  When the fire alarm is in a state of alarm, it unlocks all the stairwell doors.  Two conductor wire is run from the fire alarm panel contacts to a special fire alarm relay in the power supply that powers the electric locks on the stairwell doors.  The alarm panel opens the circuit, causing the state of the fire alarm relay to change, thus powering down the fail safe locks and thereby leaving them unlocked.

An important detail:  technically speaking, according to most building and life safety codes, fire rated doors can only be modified in a fire rated shop.  Therefore if you field cut a raceway for an electric wire through the cross members of the door, for example, you are probably voiding the fire rating.  I have never heard of anyone being called on this, but it is good to keep in mind.  Just like it is good to keep in mind that the AHJ has total authority over what you can or can’t install.  Best make sure you’re on the same page with her or him, otherwise they do have the power to make you remove what you installed and replace both door and frame to repair the damage.

Happy hardware and good luck to you.

*Some jurisdictions specify that not all stairwell doors need be unlocked in the event of a fire, only certain doors.  For example, I have known some places where code was the door had to be unlocked at every fourth floor.  Check with your local AHD to find out what the rules are for your location.

Multi-function Doorways, Part One

As seen in Doors and Hardware Magazine.

Whenever something is invented, humans find more uses for it.  This is certainly true for door automation and electric locking.  It was not long after people realized a door could be unlocked remotely using an electric strike and a door could be opened automatically using a power operator (automatic door opener) that they began using these devices together.   Of course this combination of devices was soon interfaced with intercoms.  Exit devices with electric latch retraction and electromagnetic locks were thrown into the mix, as well as access control, delayed egress and/or security interlock systems.  Any of these systems alone is sufficient to complicate an installation, but when you start to use several on one opening, that’s when things really start to get interesting.

A hospital can be one of the best places to run into a doorway that needs to perform many functions (pun intended).  Hospitals seem to have more varied reasons to keep different people out at different times, or to let them in or out by different means.  In addition to standard life safety and security issues, hospitals also have to anticipate the needs of patients who may be under the influence of medication and/or mental disorders and/or have physical limitations.  Some patients must be kept inside for their own safety while all patients must be able to exit swiftly and safely in the event of a fire.

Let’s use as an example a hospital emergency ward entrance used primarily by ambulance drivers.  The hospital wants only ambulance personnel and the security guard  to be able to activate the power operator, and to control access by use of a remote switch operated by the security guard  for the general public and an access code by hospital employees (other than ambulance personnel).

Since it is a pair of doors, concealed vertical rod exit devices are the most efficient, safe and secure way to lock them and provide reliable free egress in the event of an emergency.  However, since there is a power operator involved, these devices must be equipped with electric latch retraction; and since use of the power operator was to be limited, a second electric means of opening the door would be required.

A simple way to solve the problem of the second means of unlocking is by using electrified exit device lever trim with one of the concealed vertical rod exit devices.  Persons not requiring the power operator can get in by using the access control, or the security guard  can “buzz” them in using one of two remote buttons.  Because there will be two means of unlocking the door electrically, the security guard  will need a small desk unit with two buttons:  one that activates the power operator and electric latch retraction and one that activates the electric exit device trim.

Below is an amateur wiring diagram (made by me) of how, basically, the system works.

Central to the concept is an access control device with two relays and a request to exit input.  This allows several of the connections to be made through the access control system.  If the access control system on site does not provide more than one relay, the same functions can be accomplished by using additional relays in the power supply.

The system as shown in my illustration above works like this:

Ambulance personnel activate the power operator using the access control system.  The access control system signals the power operator via contact closure in Relay #1.  The power operator triggers the relay in the power supply to retract the latches of the exit devices, then opens the door.

Other authorized hospital personnel use the access control system to unlock the lever trim.  The access control system changes the state of Relay #2, triggering the relay in the power supply to unlock the trim.  They turn the lever, pull the door open and walk in.

Injured people arrive on foot at the Emergency Room entrance.  The Security Guard sees them (or is notified by intercom, not shown) and lets them in by pressing the red button, activating the power operator, or by pressing the green button that unlocks the exit device trim.

There exist many possible variations of this system.  Knowledge of access control systems and door hardware are required, but the most important principal in play is the use of contact closure to signal multiple devices.

The Elusive “Touch Chip” Credential

A few years ago, Ingersoll Rand (IR) purchased Locknetics Security Engineering in Connecticut, and since then gradually rebranded the line as Schlage Electronics.   A little over a year ago, as part of the process of closing the Connecticut facility, Schlage Electronics started phasing out its TR80 and TR81 touch readers.  These readers were based on the old technology of the Dallas chip, otherwise known IR/Locknetics land as the touch chip or iButton.  By the end of 2010, Schlage phased out all commercial electronic locking products that incorporated touch chip readers, such as touch readers and locking technologies that incorporated the touch reader, such as the CM line of computer managed locks and their electromagnetic locks with on-board access control.

When the new price books were released in January 2011, the touch chip credential was completely absent.   When questioned about legacy systems, representatives from IR indicated that touch chip users should migrate over to prox tags.  With the new AD and CO series electronic locks, Schlage made available new software and a new hand held programmer (the HHD-KIT) that is backwards compatible with the old hardware.  They also produced a tag with a prox chip on one side and a touch chip on the other so that legacy facilities would be able to carry both credentials over the period of years during which the old CM or other series locks would age out of the system.

One might think that the touch chip has completely faded from the Schlage Electronics scene, but such is not the case.  Looking through the Multi-Family Price Book what do I discover but the new SRT-100 touch reader and a barrage of “iButton” touch chip credentials such as the one pictured.   The new CT-5000 controller that replaces the old CT-1000 controller is also available for those who need to replace ailing legacy systems.  It is my understanding that the iButtons that appear under the multi-family division are fully compatible with legacy technologies such as CM locks or KC-2 series locks.

There is also a new line of smart residential locks that incorporate touch chip technology.  So it is safe to say that touch chip technology is not going to disappear anytime soon.  So if you have a large facility full of old Locknetics products that take iButtons, don’t panic.  At least for now you can still get them.


Interconnected Locks


Sargent 7500 Series Interconnected Lock

An interconnected lock is actually two locks that are connected by an assembly that retracts both the deadbolt and the latch simultaneously when the inside handle is turned.   This is done to fulfill the life safety requirement under NFPA 101 that egress should be accomplished by one motion with no prior knowledge necessary, and at the same time provide the user with the security of a deadbolt.  The same function could be provided by an entry function mortise lock, but interconnected locks are cheaper, since they are usually cobbled together out of (usually) a grade 2 cylindrical lock and a tubular deadbolt.

The history of the interconnected lock is a twisted, strange story of different companies reinventing the wheel with different distances between the centerlines, connected or separate latch/bolt assemblies with correspondingly different strike preps, and radically different hole patterns on both interior and exterior door surfaces.  The end result has been many, many doors and frames prepped for locks that are now irreplaceable.

Today, preps are much more standardized.

These are some of the interconnected locks available today and the measurements of their preps:

  • Falcon H Series – 4 inches CTC, 1-3/4 inch hold above, 2-1/8 inch hole below
  • Schlage H Series – 4 inches CTC, 1-1/2 inch hole above, 2-1/8 inch hole below
  • Schlage S200 Series – 4 inches CTC, 1-1/2 inch hole above, 2-1/8 inch hole below
  • Schlage CS200 Series – 4 inches CTC, 2-1/8 inch holes above and below
  • Sargent 75 Series – 4 inches CTC, 2-1/8 inch holes above and below
  • Yale 4800LN series – 4 inches CTC, 2-1/8 inch holes above and below

Replacing any of the locks above with any of the others would not present an enormous problem.


Sargent 7500 Series Door Prep

PS900 Series Schlage Electronics and Von Duprin Power Supplies Demystified

Von Duprin and Schlage Electronics are divisions of Ingersoll Rand. Both are major manufacturers of power supplies for use with electric locking systems and access control. As of January 1st, 2011, Ingersoll Rand discontinued two of their power supply product lines, the PS800 series Von Duprin and the Schlage Electronics 500 series, and merged them into the new PS900 series.

A split in power supply branding may or may not remain, depending on what document you are looking at, but whether they say they are Schlage or Von Duprin, they are all the same PS900 series.

Here is the lineup:

PS902 – 2 Amp output at 12 or 24VDC, field selectable

Compatible with these option boards:

  • 900-BBK: Battery Backup – back up power in case of power outage, includes batteries
  • 900-FA: Fire Alarm – relay for interface with fire alarm panel  – wires to main board
  • 900-2Q: 2 Relay QEL control Board – to run 2 Von Duprin QEL devices
  • 900-4R: 4 Relay Output Board – four relay outputs to operate 4 electric locking devices, not QEL or EL
  • 900-4RL: 4 Relay Logic Board – for man trap or security interlock systems
  • 900-8F: Fused 8 Zone Distribution Board – 8 outputs, fused for circuit protection
  • 900-8P: PTC 8 Zone Distribution Board – 8 outputs, circuit breaker protected
  • PS902 can accommodate 1 of the above option boards in addition to the 900-FA option and battery backup.

    For use with electric locks and with Von Duprin Quiet Electric Latch retraction (QEL) exit devices, but NOT with Von Duprin electric latch retraction (EL) exit devices.

    PS904 – 4 Amp output at 12 or 24VDC, field selectable

    Compatible with these option boards:

  • 900-BBK: Battery Backup – back up power in case of power outage, includes batteries
  • 900-FA: Fire Alarm – relay for interface with fire alarm panel  – wires to main board
  • 900-2Q: 2 Relay QEL control Board – to run 2 Von Duprin QEL devices
  • 900-4R: 4 Relay Output Board – four relay outputs to operate 4 electric locking devices, not QEL or EL
  • 900-4RL: 4 Relay Logic Board – for man trap or security interlock systems
  • 900-8F: Fused 8 Zone Distribution Board – 8 outputs, fused for circuit protection
  • 900-8P: PTC 8 Zone Distribution Board – 8 outputs, circuit breaker protected
  • PS904 can accommodate up to 2 option boards and battery back up.

    Note:  no plug-in for fire alarm relay on main board.  900-FA is only usable with the PS904 if used with an option board.

    For use with electric locks and with Von Duprin Quiet Electric Latch retraction (QEL) exit devices, but NOT with Von Duprin electric latch retraction (EL) exit devices.

    PS906 – 6 Amp output at 12 or 24VDC, field selectable

    Compatible with these option boards:

  • 900-BBK: Battery Backup – back up power in case of power outage, includes batteries
  • 900-FA: Fire Alarm – relay for interface with fire alarm panel  – wires to main board
  • 900-2Q: 2 Relay QEL control Board – to run 2 Von Duprin QEL devices
  • 900-2RS: 2 Relay EL Control Board – to run up to 2 Von Duprin EL devices
  • 900-4R: 4 Relay Output Board – four relay outputs to operate 4 electric locking devices, not QEL or EL
  • 900-4RL: 4 Relay Logic Board – for man trap or security interlock systems
  • 900-8F: Fused 8 Zone Distribution Board – 8 outputs, fused for circuit protection
  • 900-8P: PTC 8 Zone Distribution Board – 8 outputs, circuit breaker protected
  • PS906 can accommodate up to 3 option boards, fire alarm interface (with option board) and battery back up.

    For use with electric locks and with up to 6 Von Duprin Quiet Electric Latch retraction (QEL) exit devices, but NOT with Von Duprin electric latch retraction (EL) exit devices.

    PS914 – 4 Amp output at 12 or 24VDC, field selectable

    Compatible with these option boards:

  • 900-BBK: Battery Backup – back up power in case of power outage, includes batteries
  • 900-FA: Fire Alarm – relay for interface with fire alarm panel  – wires to main board
  • 900-2Q: 2 Relay QEL control Board – to run 2 Von Duprin QEL devices
  • 900-2RS: 2 Relay EL control Board – to run up to 2 Von Duprin EL devices
  • 900-4R: 4 Relay Output Board – four relay outputs to operate 4 electric locking devices, not QEL or EL
  • 900-4RL: 4 Relay Logic Board – for man trap or security interlock systems
  • 900-8F: Fused 8 Zone Distribution Board – 8 outputs, fused for circuit protection
  • 900-8P: PTC 8 Zone Distribution Board – 8 outputs, circuit breaker protected
  • PS914 can accommodate 2 of the above option boards, plus fire alarm interface (on one of the boards) and battery back up.

    Capable of powering:

  • Up to 4 Electric Latch retraction (EL) exit devices with 900-4RL board
  • Up to 2 EL devices with 900-2RS board
  • Up to 4 Quiet Electric Latch retraction (QEL) exit devices
  • Up to 4 Chexit (CX) delayed egress exit devices off the main board (use 900-8FA combination board if Fire Alarm relay is required)
  • Electric locks or strikes

    Ordering Tips:

    PS-914 is a 4 Amp power supply that is double the capacity of the old PS873, however, from my conversation with IR tech support, their feeling is that it is prudent to power no more than 4 EL devices per PS-914.  Theoretically the power supply could support as many as 8 EL devices however this presents the challenge of timing the relays so that no two can change states at the same time.  If two EL devices are powered up simultaneously the PS-914 could be damaged.

    None of the PS900 series power supplies are a drop-in replacement for their predecessors, and the old and new option boards are not cross-compatible with the old and new power supplies.  Therefore, replacing old power supplies with new can present a rewiring challenge.

    Ordering back-up batteries can be a little tricky, since they have very similar part numbers for the batteries, the charging circuit board, and a set that includes the board and the batteries.

  • 900-BAT – Pair of batteries only
  • 900-BB – Battery back up board only
  • 900-BBK – Power battery back up kit, board and batteries


    Deadbolts and Auxiliary Deadlocks


    There are three main types of deadbolts:

    • Tubular (or Cylindrical)
    • Rim (surface mount)
    • Mortise

    This article discusses the installation details and relative merits of each, as well as what to look for in terms of quality and security.

    Deadbolts are usually considered an auxiliary lock because, with the exception of aluminum and glass storefront doors, they are not the primary means of latching the door shut.

    Tubular Deadbolts

    Above is a the first page of the B600 Series section of the Schlage commercial price book, showing an exploded view of the B600 series deadbolt.  Notice the “Security Shield” that protects the bolt from attack through the door.

    Tubular (or cylindrical) deadbolts are by far the most popular deadbolts used today.   Preferred by renovation contractors for their ease of installation, they differ greatly in quality and security.


    Tubular (or cylindrical) deadbolts are generally installed into a modified 161 door prep – that is, the same prep that accepts a standard cylindrical doorknob or lever set.  The 161 prep consists of a 2-1/8 inch diameter hole drilled through the door.  This hole is called the “bore.”   A second hole, called the “cross bore,” is then drilled from the lock edge of the door to intersect with the bore.  This second hole is usually 7/8 or 1 inch in diameter and is located on the center line of the first hole.  See diagram:


    Quality and Security

    Quality in tubular deadbolts ranges from the relatively poor quality of inexpensive locks widely available in lumber yards and hardware stores to high security versions available mainly from locksmiths and other security hardware specialists.  The differences between cheap and good are:

    • Sturdiness of the bolt
    • Strike reinforcement
    • Guarding of the bolt
    • Sturdiness of the cylinder collar
    • Bump, pick and drill resistance

    The bolt is the actual part that projects out of the door and into the door frame.   The sturdier it is, the harder it will be for a burglar to break it off or saw through it.

    The strike, or strike plate, is the rectangular piece of metal in the door frame that receives the bolt.  In a wooden frame, this piece will only be as strong as the wood it is attached to.  This is why it is important that the strike fasteners are long enough to reach the stud behind the frame.

    The dust box goes inside behind the strike plate, inside the door frame.  A metal dust box makes it much more difficult to get a tool behind the end of the bolt – a very important function in terms of burglary resistance.

    On a steel door frame the strike plate becomes less important, but it is still important to guard the end of the bolt as effectively as possible.

    The cylinder collar is the washer-like ring that surrounds the cylinder and rests against the exterior surface of the door.   The best deadbolts have solid collars that spin freely if one tries to twist them off with pliers.   Cheap deadbolts have hollow collars that crush like a beer can when gripped by pliers.

    Since key bumping videos are now widely available via the Internet, it is worthwhile making sure your locks are bump resistant; lock picking is more of an art, but some burglars are skilled in it, so pick resistance is worth having; and because cordless drills are inexpensive and readily available, drill resistance is a good thing, too.   Locks that are resistant to these three kinds of attacks have a UL Listing UL437 for Burglary Resistance and say so on their labeling.  Two deadbolts that offer UL437 burglary resistance as well as sturdy bolts, collars and provisions for strike reinforcement are the Schlage B600 series with Primus or Everest UL437 cylinder, and the Medeco D11 series with M3 series cylinder.

    Rim Deadlocks

    The terms “deadlock” and “deadbolt” are often used interchangeably.

    Surface mounted deadbolts, AKA rim deadlocks, were once the industry standard.   Many locksmiths’ fortunes were made on the Segal 667 “jimmy proof” deadbolt with cylinder and latch guards, and, in fact, that locking system was often effective in keeping burglars out.  My personal preference for maximum locking strength (short of a multi-point lock) is a jimmy proof rim deadbolt and a tubular deadbolt on the same door.

    Here is an illustration of the Segal vertical deadbolt:

    A jimmy proof deadbolt, otherwise known as a vertical deadbolt, is the most effective kind of rim deadlock because it interlocks the door and frame in a way that few other locks do.

    The other kind of rim deadlock is a horizontal deadbolt such as the Yale 112 (see below left).

    The Yale 112 features a 1-1/2 inch throw deadbolt – ½ inch longer than what is normally available in a tubular deadbolt.

    To achieve bump, pick and drill resistance in a rim deadlock, simply add a UL437 UL listed rim cylinder.  Protect the cylinder with a cylinder guard to increase security still further.

    The weakest part of the rim deadlock is the strike when it’s installed into a wooden frame.  To help alleviate this weakness, install screws that are long enough to reach the stud behind the door frame.

    On a metal frame, a rim lock strike can be very strong when it is installed correctly.

    Mortise Deadbolts

    There are two kinds of mortise deadlocks:

    • Small Body Mortise Deadbolts
    • Full Size Mortise Deadbolts

    Small body mortise deadbolts are usually installed where most auxiliary locks are installed, six inches to a foot above the primary lock, maybe around 60 inches from the bottom of the door frame.  The lock case of a small body mortise lock is variable – that is, it is not standardized.

    A small body mortise deadbolt can be a good choice for a wooden door, especially if it is a thicker-than-usual wooden door.  Since the lock is a good size metal box that gets tucked into an approximately 5 inch by 1/2 inch pocket carved into the wood, the lock utilizes the strength of the door to its best advantage.

    Full size mortise deadbolts are installed in an “86 prep” (see illustration), which is a pocket located on a center line about 40 inches above the bottom of the door frame.  Unlike most other deadbolts, full size mortise deadbolts are intended for use as the primary – and usually the only – lock on any given door.  Full size mortise deadbolts are usually used on mechanical compartments, closets in corridors or other places where trim would be in the way.

    Both small body and full size mortise deadbolts feature heavy duty mechanisms and strong, 1-inch projection bolts.  With the addition of a high security, UL437 UL listed mortise cylinder to add bump, pick and drill resistance, mortise deadbolts can provide a high degree of security.


    Schlage L460 Series Small Body Mortise Lock


    Understanding Door Security Monitor Switches

    A number of different kinds of switches are available to help you keep track of whether or not your door is shut and / or locked.  Here are some of them:

    Door Status Monitor Switch

    A door status monitor switch changes states when the door is opened or closed.  Typically this is accomplished by using a magnetic reed switch, either surface mounted or concealed in the edge of the door and door frame like the one shown at right.

    How a Magnetic Reed Switch Works

    The magnetic reed switch is typically installed on the door frame and the magnet that activates the switch is typically installed on the door.   Inside the magnetic reed switch, a thin piece of steel – a steel ‘reed’, if you will – is held in position by the attraction of the magnet when the door is closed.  When the door is opened, the magnet is taken away from the switch and the spring tension of the “reed” causes it to spring back against the other contact, changing the state of the switch.

    Most magnetic reed switches are normally closed – “closed loop” – but are also available normally open (“open loop”) SPDT (single pole double throw, or “form C”) or DPDT (double pole double throw).

    The Purpose of the Door Status Monitor Switch

    The door status monitor switch is used to notify remote devices that a door is open or closed.  Typically these remote devices are burglar alarm panels or access control system controllers.   It does not tell you if the door is locked, just if it is closed.

    Request to Exit Switch

    The request to exit switch, also known as a REX switch, is so named because it is usually connected to the request to exit contacts on an alarm panel or access control board.  It is used to notify an external device that someone is exiting through, or wants to exit through, a door.  REX switches come in a wide variety of configurations, from push button palm switches engraved “push to exit” to switches concealed inside exit devices.  A motion exit sensor is also a form of request to exit switch.

    Request to exit switches are available with a wide variety of contact configurations and with or without electronic or pneumatic time delay.   If the switch is being used as a means of egress for pedestrian traffic, it will need to comply with life safety code.  Life safety code varies from locality to locality as governed by your local AHJ – Authority Having Jurisdiction – that is, your local building inspector or fire marshal.

    Latch Bolt Monitor Switch / Strike Monitor Switch

    I write about Latch Bolt Monitor (LBM) switches and Strike Monitor Switches because they somewhat overlap.  Both are designed to monitor the position of the latch bolt.

    Some LBM switches are inside locks and others are in electric strikes.  From inside the lock, they monitor whether the latch is extended or depressed.  When located in an electric strike, they monitor whether or not there is a latch bolt present in the keeper.

    Pictured at right is Securitron’s line of inexpensive strike monitor switches as examples of strike monitor switches.  Several companies offer like products.  Strike monitor switches are an easy way to monitor if there is a latchbolt (or some other object) present in the keeper.   Several companies, such as Von Duprin, offer heavier duty monitor strikes.  Monitor strikes are sold as a finished unit that includes as strike and a switch whereas strike monitor switches are aftermarket add-on units.

    Magnetic Bond Sensor / Bond Sensor

    Magnetic bond sensor and bond sensor options refer to electromagnetic lock applications.  Many manufacturers offer Bond Sensor or Magnetic Bond Sensor as an option.  What this does is allow an electromagnetic lock to notify some external device that its holding force is below spec.  Authorities are alerted and the situation is addressed.

    Maximizing Effectiveness

    To maximize effectiveness of door monitor switches, it is best to use both a door status monitor and some kind of lock status monitor as well, and this is why:  because monitor switches can be fooled.  A door status switch will tell you if the door is open or closed – unless it has been altered to tell you the door is closed when it is not.  Also, a door may be closed, but not locked.  If you have a latch bolt monitor or magnetic bond sensor in place as well as a door status switch, you will know if the door is closed but not locked.

    This is the center of this knowledge:  to know that the door is shut AND locked.




    How to Choose a Door Closer

    To intelligently choose a door closer for your application you have to know certain facts:

    • Does the closer need to comply with ADA opening force guidelines?
    • Is the door an interior or exterior door?
    • What is the door width?
    • Will the closer be mounted on the push or pull side of the door?
    • Where on the door will the door closer be installed?  How much room is there?
    • Are there any special circumstances like wind, positive or negative pressure, etc.?
    • You may also need to know the door handing.

    ADA Reduced Opening Force Guidelines

    American Disabilities Act (ADA) reduced opening force restrictions are enforced by the Authority Having Jurisdiction in your locality.  In some localities or applications ADA requires a maximum opening force of 5 lbs. and in others a maximum opening force of 8.5 lbs.  Most closers on the market today can be field adjusted to comply with these restrictions, but to do so you need to have a door pressure gauge.

    I am mildly acquainted with two door pressure gauges.  One is the model DPG by HMC and the other is the ADA/FG by LCN.  Apparently there are a lot of initials involved in door pressure.

    Door closers are also available with reduced opening force meant specifically to comply to ADA standards.

    Manufacturers usually print a disclaimer that says that a door closer adjusted to ADA maximum opening force may not have enough power to shut the door.  This is often true because perhaps recommended spring strengths for different applications are the result of perhaps a century of innovation.  Manufacturers know that a force greater than 8.5 pounds may be necessary to close a door.

    Interior versus Exterior

    When speaking about door closer closing force, we say that a door closer is of a certain size.  Door closer size does not refer to actual dimensions, but to spring strength.  Historically, door closers are available in sizes 1 through 6 – 1 being the wimpiest and 6 capable of exerting the strongest closing force.

    A size 4 closer is usually recommended for an exterior, 3-foot wide door, whereas a size 3 closer is deemed appropriate for an interior door of the same dimensions.  The assumption here is that the exterior door is more likely to be expected to close a door against a wind or negative or positive air pressure.

    Door Width

    If you look at a door hung on butt hinges and equipped with a door closer from above, it looks something like this:

    View from the Ceiling


    You see from the illustration that the door closer closes the door by exerting force on a point about eight or ten inches from the hinge side of the door.  To see what this means, go to a door with no door closer.  Open it.  Now put your hand a foot from the hinge side of the door and push it closed.  Pretty difficult, isn’t it?   If your door was wider, it would be even harder to close from that point.  This is why door closer size – that is, spring strength – is determined by the width of the door rather than the height.

    For a three foot wide exterior door, you would normally adjust your door closer to be a size four.  For a four foot wide exterior door you would adjust your door closer to be a size five.  Therefore, if you have a four foot wide exterior door, you had better buy a closer that can be adjusted to a size five.

    Push or Pull?

    Different arms are required for different applications.  On doors that swing out, where the closer is mounted on the push side, the closer is mounted in a top jamb or parallel arm configuration.  If it is mounted on the pull side it is mounted in what is called a ‘standard’ installation.  (There are other ways to mount a closer on the push side, but parallel arm and top jamb are the most common.)

    See manufacturer’s literature for more information, or check out my article on Door Closer Basics.


    If you have a glass and aluminum storefront kind of door, you may have a space issue as regards your choice of door closer.  If you have a hollow metal door with no window hung in a steel frame, chances are you will have no space issue.

    You need to figure out what door closer will fit.  To do that, measure the space where you would like to install it and download installation templates or instructions from manufacturer’s web sites.  Check the dimensions to see if the closer you have selected will work or not.

    Or you can measure your door and frame and consult a door hardware professional.

    Special Circumstances

    I have installed door closers in some fairly challenging environments.  One, for example, was on a four foot wide, eight foot high, two and a quarter inch thick mahogany and glass door.  In addition to the size of the door, the location was also challenging – right across Beacon Street from the Boston Common where the wind could race across the open ground and dash itself against the door to its heart’s content.  Also, the front of the building had settled over the century or so of its existence, and leaned decidedly inward.  The door opened inward, and, left on its own, would swing sedately inward to 90 degrees if not latched.

    In other words I had to install a door closer that would close an extra heavy door, uphill, in a wind.  I actually got one that would do it about 95% of the time.  For this application I chose the most durable, powerful, adjustable door closer I knew at the time:  the LCN 4041.  If I did the same job today I would probably choose an LCN 4011 or a Norton 7500.

    A big, beefy, versatile door closer is not a cure-all.  For example, sometimes the 4041 is just too big, or templated too close to the hinge.  The point is that you must look at all the details of your door before you buy a door closer – not only how it is made and its size, but its environment as well.


    What’s Hot in Door Hardware

    A couple of new innovative products have recently caught my attention.  Here they are:

    Security Door Controls (SDC) Model LR100VDK:

    Field Installed Electric Latch Retraction Retrofit Kit for Von Duprin Exit Devices









    This product is available now.

    The mere 450mA inrush powering Security Door Controls’ new electric latch retraction retrofit kit is attractive enough.  Its compatibility with all Von Duprin touch bar style devices may make it just about irresistible.   Optional request to exit switch kits are available.  The unit is usable for access control and electric dogging applications.

    The small inrush is huge.  (I always wanted to say that.)  High inrush electric latch retraction requires special, expensive power supplies.  Not so with the LR100VDK.  Your average regulated and filtered 1-amp 24vdc power supply will do nicely, thank you.

    Another great aspect of this kit is that it is compatible with the Von Duprin 22 series exit device. So now, for relatively short money you can give a customer electric latch retraction in a decent quality exit device.

    HES Model 8500 Electric Strike for Mortise Locks

    This product is due to become available by the end of August, 2011, but we’ll see.

    Hanchett Entry Systems’ new lipless electric strike solution for mortise locks.

    Installing an electric strike to release a mortise lock will be much easier with the HES 8500 since no cutting of the face of the frame is necessary.  Below is an illustration showing the difference between the HES 1006 standard electric strike for mortise lock and the new HES 8500.

    HES 1006 prep for hollow metal

    HES 8500 door prep for hollow metal - look ma, no lip!













    This is not a new idea, but installers seem excited about the prospect of having an alternative to the Securitron UnLatch, which has been around for quite some time.  The Unlatch model that the HES 8500 will compete with will be the Securitron MUNL.

    Of course, the advantage the MUNL currently enjoys is that, unlike the 8500, one can actually buy an MUNL.  Comparatively, the Securitron requires a door frame depth of about 1-7/8 inches whereas the the 8500 will require about 1-3/8 inches.  The 8500 will draw 240mA at 12 volts DC and 120mA at 24 volts DC and draws no inrush current.  The MUNL has an inrush of 2 amps at 24vdc or 4 amps at 12vdc and an operating current of 600mA at 12vdc or 300mA at 24vdc.  One important result of the lower current consumption of the 8500 will be that instead of the 4 amp 12vdc or 8 amp 24vdc power supply necessary for each MUNL, one 8 amp 24vdc power supply will theoretically power as many as perhaps 60 of the new HES 8500.  Of course then, factors like wire run will come into play, but still.

    Another positive attribute will be that the 8500 will be field selectable for fail safe or fail secure whereas the MUNL requires an additional module to make it fail safe.

    All in all, the 8500 seems that it will be a better choice all around.  We’ll just have to wait and see how it performs in the field after it becomes available at the end of August 2011.