What a card reader door needs behind the wall

A card reader door is a small system, not a gadget

When a card reader goes onto a wall, it looks like a single device. In reality it is the visible end of a chain. A credential is presented to the reader. The reader sends a signal along a cable to a controller. The controller checks the credential and, if it is allowed, sends power to the lock. The lock releases. A sensor notes that the door opened, and a device inside the door lets people leave. If any link in that chain fails, the door misbehaves.

Owners sometimes assume the work is finished when the reader lights up and beeps. A door that reads the card but does not release because the strike is misaligned, or a door that unlocks but then relocks before anyone has opened it, is not a working door. The test is not whether the reader works. It is whether the door works for the people who use it, every day, in all conditions.

The goal of this page is to explain, in plain language, the parts behind the wall so that you can ask good questions and understand a proposal. It builds on the overview in the page on access control for small business doors, and focuses on the door itself.

Quotes are given by phone. A card reader door usually needs an on-site look before pricing, because the wiring route, the door construction and the existing hardware vary. A service call charge applies to dispatch, and it is explained before anyone is sent.

Choosing the lock: electric strike, magnetic lock or electrified lockset

There are three common ways to make a door respond to a card reader. The first is an electric strike. A strike is the plate in the door frame that the latch or bolt engages. An electric strike replaces it with a version that can release on command, so the door can be pulled open without turning the handle or key. Between releases, the latch is held. The door's existing lockset still works from the inside, which can simplify the exit question. The page on electric strike installation overview covers the details.

The second is an electromagnetic lock, a large magnet mounted on the frame that holds an armature plate on the door. When power is applied, the door is held shut. When power is removed, it releases. Maglocks have no moving parts to wear out, but they rely entirely on power and have strict requirements about how people exit. The page on magnetic locks and fire egress explains why.

The third is an electrified lockset or an electrified exit device. The lock itself has electronics inside, so the handle or the push bar is locked or unlocked electrically. These are common on commercial doors that already have a strong mechanical lock and where a clean installation without exposed parts is wanted. They require power to reach the door, often through a hinge that carries wires or a transfer device.

Which is right depends on the door, the frame, the level of security and the rules for exit. A narrow stile glass door often cannot take a standard strike and may need a mortise lock with a built in electrical release or a maglock. A hollow metal door in a steel frame usually accepts a strike easily. A wooden door may need reinforcement. A technician looks at the actual door before recommending one.

Fail-safe and fail-secure: what happens without power

Two terms decide how a door behaves when electricity stops. A fail-safe lock unlocks when power is removed. A fail-secure lock stays locked when power is removed. The names describe the safety of people, not of property. Fail-safe protects people by opening, and fail-secure protects property by staying shut.

A magnetic lock is naturally fail-safe, because it needs power to hold. An electric strike can be either. A fail-secure strike keeps the latch captive until power releases it, which means that during a power failure the door stays locked from outside but can still be opened from inside by turning the handle, since the lockset's own mechanical action is separate. A fail-safe strike releases when power is lost, leaving the door unlocked.

The right choice depends on the door's job. A main entrance in a building where life safety is the priority may favor an arrangement that releases in an emergency. A door protecting a storage room full of stock may favor one that stays locked during a power failure, with a reliable way to leave. Often the decision involves the fire authority, because doors that serve as exits are covered by rules that override a business's preference.

It also depends on how long the system can run on backup. A power supply with a battery keeps the reader, the controller and the lock operating for a time during an outage. After the battery runs down, the lock reverts to its fail state. In a hurricane season climate, where outages can last, a business should know what its doors do on day two of a power loss, not just in the first minute.

Ask the installer to state, for every door, which fail state is used and why, and to show it by cutting power during testing. A door whose behavior is only assumed is a door with a surprise waiting.

Getting out: egress and the request to exit

People must be able to leave through any door on an exit route without hunting for a card or knowing a secret. The way a door achieves this depends on the lock type. With a strike and a normal lockset, the inside handle retracts the latch and the person walks out. No electronics are involved in leaving. This is a major advantage of strikes on doors that serve as exits.

With a maglock, there is no latch to retract, so the exit must be provided by other means. A request to exit device, usually a button or a motion sensor on the inside, cuts power to the magnet when someone approaches to leave. For safety, a maglock on an exit route generally also needs a manual release that does not depend on the electronics, and a connection to the fire alarm so that the door releases when the alarm sounds. Those arrangements are decided according to local rules, and the installer should explain which apply to your door.

A request to exit device has another job. It tells the system that the door is being opened from inside by an authorized action, so the system does not treat the opening as a forced door and raise an alarm. Without it, a door that opens from inside could trigger a forced entry alert every time someone leaves.

Think about people with limited mobility as well. Hardware must be usable without tight grasping, and doors need to open without excessive force. A small business with customers or visitors should consider how the reader, the push button and the door's closing force serve everyone.

Whenever a door is on an exit route, the safe course is to consult the local fire and building authority or a qualified professional about what is permitted. A locksmith can install and service hardware within the arrangement that is approved for the building, but cannot waive requirements.

Power: the supply that everything depends on

Electric locks and readers draw power, and it must be delivered at the right voltage and with enough capacity. Most systems use low voltage direct current, commonly twelve or twenty four volts, supplied by a power supply in a closet or ceiling space. The supply must be sized for all the devices it feeds, with allowance for peaks when locks engage.

A battery backup is a sensible addition. When mains power fails, the battery takes over so the doors keep working. Batteries age, and they need replacing. A business that installs a system with a backup should ask when the battery should be checked, and who will do it. A neglected battery is worse than none, because it gives false confidence.

Wire size and length matter. Voltage drops along a long cable, and a lock at the end of a long run may receive too little power to operate reliably. The installer must choose a cable gauge suited to the distance and load. A door that works in the morning and fails in the afternoon when the lock heats up may be a symptom of marginal power.

Protection is worth planning. Electric locks can create voltage spikes when they switch off, which can damage electronics unless suppressed. A good installation includes the right protective components. Surge protection on the supply and, where practical, on the incoming power helps in a region with frequent thunderstorms.

Finally, tell the installer where mains power is available and where the controller can sit. A power supply needs ventilation and access for maintenance. Putting it in a locked utility closet, rather than above a ceiling tile in a public area, protects it from tampering and from heat. If your building has shared electrical rooms controlled by a landlord, arrange access in advance.

Wiring paths and building construction

Getting wires to the door is often the hardest part. A card reader typically needs a multi conductor cable to the controller, and the lock needs power wires. A door position switch and a request to exit device need their own conductors. In a building under construction, these are run before the walls close. In an existing building, they must be fished through walls, ceilings or conduit.

Miami buildings are often concrete block, and many have concrete ceilings. Running cable through solid concrete is difficult, so installers use surface mounted raceway, existing conduit or ceiling spaces where available. Surface raceway is neat when done well and can look out of place when done carelessly. Ask what the installation will look like and where cables will run.

Getting power across the hinge side of the door to a lock mounted on the door is another challenge. Options include a concealed hinge with wires, a loop of flexible cable in a protective sleeve, or a transfer device that passes power through the door edge. Each has trade offs in appearance and durability. A glass door with a pivot may need a different solution altogether.

Existing doors must also be prepared. A strike needs an opening cut in the frame, and a frame that is warped, weak or full of old paint may need repair first. A hollow metal frame can usually be prepared neatly. A wooden frame may need to be built up. Aluminum storefront frames require hardware designed for them. The page on storefront door lock repair explains why narrow stile doors are a distinct case.

Plan for the future. Running a spare conductor or two, or leaving room in the raceway for an added device, costs little at the time and saves effort later.

Door condition and the quiet failures

A card reader door can fail for reasons that have nothing to do with electronics. A door that sags drags the latch against the strike, and the strike cannot release the latch because the latch is under pressure. A door closer that is too weak leaves the door ajar so that the lock never engages. A closer that is too strong slams the door and damages the strike. A door that was never properly aligned can make an electric strike chatter and wear.

This is why a good installation begins with the door. The technician checks hinges, the gap around the door, the latch alignment, the closer and the frame. Problems are corrected before the electronics are added. The page on door closer adjustment and replacement explains why closing speed matters for lock life.

Weather affects the system as well. A reader mounted outside faces sun, rain, salt air and humidity. Choose a reader rated for exterior use, and ask about its sealing. Corrosion of connectors is a common cause of intermittent failures in coastal areas. Using weatherproof junction boxes and sealed connectors prolongs life.

Another quiet failure is the door that is propped open. Staff prop doors for deliveries and then forget. A door position sensor with a held open alert, linked to a local buzzer or a message, helps. It is a simple feature that prevents the system from being undermined by convenience.

Finally, think about testing. After installation, the technician should test each credential, test the exit release, cut power to confirm the fail state, test the battery, and operate the door many times to confirm it latches consistently. Ask to see these tests, and keep a note of the date.

A checklist for the planning conversation

When you talk with an installer about a card reader door, bring a few clear points. Describe the door: material, frame, single or double, glass or solid, indoor or outdoor. Say how many people use it, and at what times. Explain what the door protects, and what would happen if it failed open or failed closed.

Ask about exit. How will people leave? Does the door serve as an exit route for the building? Who is responsible for confirming compliance with fire and building rules in your area? A reliable installer does not dodge the question.

Ask about the lock type and why it was chosen. Ask about the fail state and what happens in a power outage. Ask about the power supply, the battery backup and how long it will last. Ask about the wiring route and the finished appearance.

Ask about the credentials and the software. Who administers the system? What happens when a card is lost? How are users removed? What does it cost to add a door later? Ask who owns the system and whether another installer could maintain it.

Ask what the door will be like to use day to day. A lock that hesitates for several seconds, a reader that fails to read in rain or a door that does not close are the sorts of problems that make staff prop doors open. Ask to see a similar installation if possible.

Finally, be ready to share photos of the door, the frame and the area where equipment might go. Our guide on photos that help a locksmith explains which angles help. When you are ready, call and describe what you want. A technician can explain what the door needs and how an on-site visit would work.

• Door material, frame type and whether it is on an exit route
• Who uses the door and what it protects
• Lock type chosen and why, with the fail state stated
• Power supply size, battery backup and wiring route
• Testing to be shown at the end, including a power cut test

Questions people ask

Related pages

Written by Claude (AI) (AI) for 24 Hour Locksmith Miami.