Elevate your key card and key fob system with ButterflyMX


Key takeaways:

  • Key cards and fobs offer significant advantages over traditional locks and metal keys.
  • The many types of systems available — Wiegand, swipe, RFID, and proximity — increase the overall security of your property. Moreover, these access control systems provide tenants and staff with greater convenience while reducing operating costs.
  • For the best key card or key fob system, choose the ButterflyMX access control solution.
  • ButterflyMX mullion readers and keypads offer everything you want in a key or fob system but incorporate many other features your property will benefit from.


If you’ve ever stayed in a hotel, chances are you’ve used a key card to get into your room. Key fobs are an equally popular door entry device for apartment residents and office workers. Key cards and fobs are an important component of electronic access control systems, replacing the traditional lock and key.

In this guide, we review how key card and fob entry systems work, as well as the most common types of key cards and key fobs. Finally, we cover the pros and cons of setting up a key fob system and provide possible alternatives.

This post covers:


see the list of the best cloud based access control systems


What are key card and key fob systems?

Key card and key fob systems are a form of electronic access control used to manage access in and out of buildings. Fobs and key cards are electronic devices that allow authorized tenants to unlock doors. They’re a popular keyless entry system for businesses, apartments, industrial facilities, and other types of buildings.

Key card systems require three components:

  • Access credentials. Access credentials are key cards and key fobs or badges, the small electronic devices that tenants use to gain access. Fobs and cards have a built-in chip or sensor that communicates with the access reader.
  • Access reader. When a tenant holds their key card or fob up to an access reader, the reader scans it to verify their identity. After the resident is verified, the access reader instructs the door to unlock.
  • Electric or magnetic door lock. Access control systems require electric or magnetic door locks. The door lock receives a signal from the access reader to unlock, allowing a resident to enter.


What’s the difference between a key card system and a key fob system?

While key card and key fob systems are very similar, they do have a couple of minor differences.

The differences between a key card system and a key fob system are:

  • Appearance. The most apparent difference between these two systems is how each credential appears. Key card access systems use slim PVC cards that can easily fit inside a wallet or purse. They could also be attached to the end of a lanyard. As for key fob systems, the credential appears as a small plastic puck that fits on a keychain or in a pocket.
  • Use. The other significant difference between a key card system and a key fob system is how the credential is used. Key card systems are either a swipe or are triggered when in the proximity of a reader. Fobs work similarly, but sometimes they require direct contact with the reader. A property may also use its key card to double as an ID card, containing the user’s photo, title, and other related information. In these cases, maximizing the card’s use helps streamline the card access system.


Cost of key fob entry system

Key fob entry systems cost between $1,200 and $2,500 per door. The total cost depends on the technology powering your key fob system and the number of entryways you want to secure. For a more specific estimate, it’s always best to get a quote.

However, remember that these are just the costs for initial installation. Don’t forget that a residential key fob entry system will require you to purchase a steady stream of fobs as residents lose theirs, ask for replacements, or move out. Replacing key fobs costs anywhere from $50 to $400 per fob when accounting for hardware and programming time.


Watch how ButterflyMX works:


How do key fob systems work?

Key fob entry systems use wireless signals to allow cards and fobs to communicate with an access reader. If the key card provides the correct credentials, the access reader instructs the door to unlock.

Here’s how to use a key fob system:

  1. Present your credentials. First, present your credential to the access reader. Most readers are installed right next to the door. If you have a swipe card, swipe it through the reader. If you have a touchless RFID key fob, you simply hold it up close to the reader.
  2. Access reader verifies credentials. Depending on the system installed, there are different ways for an access reader to verify your credentials. For example, Wiegand key cards use a series of magnetized wires to store their credentials. Other types of cards, like proximity and RFID cards, transmit their credentials wirelessly via an electric field emitted by the access reader.
  3. Access reader unlocks the door. Finally, the access reader verifies your credentials and unlocks the door.


Types of key cards and fobs

Not all door and gate fob systems work the same. There are many types of key card and fob systems out there. Each one uses a different technology to deliver signals to the access reader. Below we share four popular types.

4 popular types of key cards and fobs are:

  1. Wiegand key cards
  2. Swipe key cards
  3. RFID key fobs and cards
  4. Proximity cards


1. Wiegand key cards

Wiegand key cards are one of the earliest types of electronic key cards. The Wiegand key card is named after inventor John R. Wiegand, who discovered a way to use magnetic polarization to encode binary data into specially made wires.

Wiegand readers emit a magnetic field. When a user swipes their Wiegand card through a reader, the magnetic field affects the wires built into the card. The reader detects these changes to the wiring to verify the user’s credentials.

While Wiegand magnetic cards began gaining popularity back in the 1970s, Wiegand technology still forms the foundation of much of today’s access control ecosystem.


2. Swipe key cards

Swipe key cards also use magnetic technology. A swipe card has a black bar, which is a strip that has been magnetized with a unique pattern. When you swipe the card through a reader, the reader opens the door if it detects the correct pattern. The technology used by swipe cards is actually very similar to how credit cards work.

Swipe cards differ from Wiegand cards because they are manufactured and encoded differently. In contrast to Wiegand cards, swipe key cards can be wiped and rewritten to interact with a different reader or lock.


3. RFID key fobs and cards

RFID key fobs and cards are named after their primary component: the RFID tag. These tags are built into the fob or card. RFID key cards use these tags to interact with card readers through radio waves.

Here’s what happens when a tenant places an RFID key fob next to a reader:

  • Signals from the access reader reach the RFID key fob. RFID card readers emit electromagnetic fields known as excite fields. The fob must be in the range of this field to unlock the door.
  • The key fob sends a signal back to the reader. When the RFID fob sends the correct credentials to the reader, the reader unlocks the door.

While most RFID access control systems consist of a standalone reader installed next to a door, you can also purchase RFID door locks. These locks have built-in RFID readers.


4. Proximity cards

A proximity card (such as NFC tags) requires the user to be in close proximity to the card reader. Like RFID key cards, proximity cards also use radio waves to communicate with proximity readers. However, proximity systems use a different radio frequency than RFID keys do.

There are two types of proximity card readers: active readers and passive readers.


Active vs. passive proximity readers

While active and passive proximity readers work similarly, there is one crucial difference.

Both types of cards require power to exchange signals with a card reader. However, active proximity cards come with their own batteries. In contrast, passive cards are powered by their proximity to the electrical field emitted by card readers.


key card system user


Applications of key fob and key card systems

Key fobs and key card systems are commonly used in hotels, but they have so many other applications across various properties.

You can find key fob and key card systems in:

  • Apartments. Key fob systems for apartments are popular because they help secure the property and its amenity spaces. Furthermore, fobs are much more secure than traditional metal keys, which can easily be stolen and copied. So rather than rekeying a lock, the property staff can deactivate the fob remotely.
  • Offices. Companies will use a key card system for offices to manage what areas employees have access to. This is especially important when protecting from data breaches or security risks.
  • Gyms. A gym key fob system is often used in gated communities or apartments where the amenity space is monetized. Those who’d like 24-hour access may purchase a fob from management rather than having to go during select hours.
  • Industrial facilities. Finally, industrial facilities use key fobs or key card systems to manage employee access and prevent threats from causing harm. That way, they can maintain a high level of security in an environment that requires it.


Should you get a key card or fob access control system?

Key card and fob access control systems are used across all property types because of their many advantages. But with all access control systems, you can expect some limitations.


Benefits of key card and key fob systems

A key card or fob system can benefit your property in the following ways:

  • Intuitive design. A simple tap of a card or fob against a reader is much easier than fumbling for a set of keys. Plus, you’ll spend less time onboarding tenants and employees with a key card or fob access control system.
  • Data collection. Building staff can monitor door usage and who’s accessing what areas with your access control system’s audit trail. In turn, your team can review the access history in the event of a security breach.
  • Elevator controls. If you need to control access to elevators in your building, a key card or key fob system prevents unauthorized visitors or tenants from accessing floors they’re not supposed to.
  • Easy administration. If a resident loses their key card or fob, staff can deactivate the card remotely to prevent a security breach or having to replace an entire lock.
  • Low maintenance. Key card and fob systems require much less maintenance than traditional locks and metal keys. For the most convenience, consider a cloud-based access control system. That way, system updates are completed remotely.
  • Cost-effective. Key card and fob systems are relatively low-cost access control solutions. The readers and credentials are inexpensive to install and replace.
  • Integration. Lastly, many of these access control systems integrate seamlessly with property management software. As a result, you can onboard employees easily while streamlining how you manage tenants.


Limitations of key card and key fob systems

Some drawbacks of a key card or fob system include:

  • Inconvenient for residents. While fumbling for a set of keys is worse than a card or fob, tenants still have to pull out a physical credential which can be annoying for some.
  • Rising expenses. When tenants lose their fob or card, they aren’t the only ones affected. Property staff must replace the lost credential to ensure tenants can access the property. The cost of replacing cards or fobs can add up quickly.
  • No guest access. Even the best key cards and fobs must be near an access reader to open doors. With a fob or card system, there’s no way for residents to grant access to guests remotely. To circumvent this issue, choose a system that offers multiple credential methods, such as a smartphone. That way, tenants can let in visitors remotely.


keypad access control smartphone


What is the best key card and key fob system?

The best key card or key fob system is ButterflyMX. Established in 2014, ButterflyMX specializes in comprehensive access control solutions, from the front door or gate to each unit and amenity space.

ButterflyMX offers two card and fob readers: the mullion reader and the keypad, which accepts both key cards and PIN codes.

The ButterflyMX access control system is filled with features your property will love:

  • Accepts multiple credentials. Equipped with 5GHz WiFi and RFID capabilities, the ButterflyMX access control system accepts different types of credentials. Choose between PIN codes, key cards, key fobs, and mobile phones. So, instead of finding a key fob replacement for your apartment or commercial space, you can offer alternative credentials.
  • Reader options. ButterflyMX readers come in two different varieties. The slim and compact mullion reader accepts key cards and fobs. The keypad reader accepts a PIN code, key card, or key fob.
  • Smart intercom capabilities. Our next-gen LED-screen intercom is the center of the ButterflyMX ecosystem. It secures your property with a 156-degree wide-angle camera, accepts multiple types of credentials, and enables two-way video calling between visitors and residents using the highly-rated mobile app.
  • Customizability. Fulfill the unique needs of your property by choosing between different intercom sizes, mount types, hoods, and pedestals. Plus, mix and match readers to fit your access needs.
  • Remote management. Manage users, credentials, audit logs, or even grant access from anywhere using the ButterflyMX mobile app. It’s simple and easy to use, giving staff the ability to work remotely if necessary.
  • Elevator controls. Tether the control of your elevator to the key card or fob system for ultimate security. When tenants use their fob or card, the system will automatically grant them access to their respective floors via the elevator. No extra steps required.
  • Seamlessly connected. ButterflyMX mullion readers and keypads work with all the other ButterflyMX products to ensure an end-to-end access control solution for your property.

But don’t just take our word for it, ButterflyMX has over 20,000 five-star reviews.


access control system

Profile image for Ferdison Cayetano


Ferdison Cayetano

I’m a proptech enthusiast from New Jersey who’s looking forward to the innovations that will revolutionize real estate.

Follow Ferdison on LinkedIn