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How Do Fobs Work?

December 7. 2016

How Do Key Fobs Work?

A key fob or ‘fob’ is the term used to refer to a small hardware device that is programmed to give access to a variety of physical objects, such as a car or building. Fobs provide the same function of traditional metal keys, as well as add a level of convenience and security for the user that the traditional key cannot.

Various fob keys


RFID Technology

Fobs work through the use of Radio Frequency IDentification, or RFID for short. RFID is an ‘intelligent’ barcode system that uses electromagnetic fields for identifying and tracking data on ‘tags’, which contain stored information. The information is passed using radio waves, hence the name Radio Frequency IDentification.

An RFID device serves the same purpose as a barcode on a product, or the magnetic strip on the back of a credit card, as it provides a unique identity to the object in question. RFID technology also employs the use of a ‘reader’ to gain the information from the tag – similar to a barcode scanner or credit card reader. RFID has the advantage of not needing such precise placement over the scanner in order to work. Whereas credit cards must be placed in their reader in an exact fashion to process the information, or a barcode scanner can take a few attempts before the code is read, RFID provides a much more user friendly experience – such as the key fob entry system. The user simply waves the fob in front of the reader, and the information can be transmitted.

RFID Tags By Grika at English Wikipedia (Self-photographed) [CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons

RFID Tags by Grika at English Wikipedia (Self-photographed) [CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons

The Fob System

To better understand how key fobs work, we will look at the example of key fobs used to enter into shared spaces in buildings, such as a condo lobby or a workplace.

While individual technologies vary based on the function required and sophistication of technology, this will outline the basic key fob system. A few items are required for this door system to function: a key fob, a reader, and a locking mechanism for the actual door.


The Key Fob

The fob itself contains a unique number implanted on a small circuit, better known as a  microchip. The microchip has a particular frequency, which communicates with the reader, allowing you access to open the door.

Each person issued a key fob has one programmed specifically for their use. For example, in a condo building where a fob is used to enter into the front door, each resident will be issued a similar item, containing the same information on the fob that allows them access. Condo employees may be issued a fob that looks identical, however it has been programmed to allow access to not only the front door, but other areas restricted to the residents.


The Reader

The reader lives up to its namesake and ‘reads’ the information contained in the key fob. Once the fob is passed in front of the reader, information is exchanged indicating whether or not access should be granted.

RFID Reader By ProtoplasmaKid (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

By ProtoplasmaKid (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

Inside the reader is a transmitter, and the key fob is adjusted to the frequency of this transmitter. This also allows for the reader to power the fob through the magnetic energy exchanged, which eliminates the need for batteries inside the fob itself, in turn allowing the fob to be quite small. The frequency of the transmitter inside the reader determines the distance required for communication with the key fob. For many access systems, a frequency of 125kHz is used.


The Locking Mechanism

The locking mechanism is the element in the system that determines whether or not access will be granted. The fob will send a signal to the reader, which in turn transmits the signal on to the door locking mechanism; if the signal sent matches the one required within the mechanism, the door will unlock. If the signal does not match an authorized pattern in the lock, the door will not open.

Depending on the level of security required in a given situation, the key fob and reader can communicate directly with the door in question, trigger the lock, and allow access. This method would work in cases such as that of a condo lobby, where the key fob is only granting access to a shared space, in which all residents are allowed.

In certain cases where a greater number of variables exist, the doors will be connected to a server that controls access to a variety of areas in the facility. This server acts as the locking mechanism, and communicates with each individual door. In this instance, each fob will be programmed specifically for the user’s security clearance. A building manager may have access to all areas, and their key fob will be programmed to allow this. Another employee may have access to only a few areas in a facility, and their key fob will be programmed as such.


Key fobs serve the same purpose as the age-old metal key; they control access to areas through the use of a door and a lock. Unlike metal keys, the fob can be programmed to be tailored specifically to a user’s needs, providing greater or more limited access to the fob holders. The use of RFID technology allows for efficient communication between the fob and the reader, providing an enhanced experience of the user. Plus, a fob can be cancelled without changing the lock, making the system more secure.


Comments (16)

  1. Bridget M. Maniscalco says:

    I have a key fob that was issued to me to enter the outer hallway of the apartment complex I live in. I bought a blank fob on Amazon. Is there a way to make it compatible with the one I have so I have an extra fob?

    1. Fob Copy says:

      Yes, we can do that for you. Just bring both in and we’ll copy it over. Hopefully we can write onto what you bought off Amazon.

  2. Lizzie says:

    I live in a condo and recently I couldn’t use my fob keys to open the doors of outdoor pool or gym. However, they still work with the main entrance, the common lounge, the garden and garage door. While none of my neighbors has the same issue. Is that possible if the management of the building limits our access to some common areas?

    1. Fob Copy says:

      It’s likely your fob is defective or the reader itself is defective.

  3. Paulette says:

    My door fob stopped working and a red light comes on when I try to use it. I was told by it was because the magnetic strip in the fob was broken. Could this be correct?

    1. Fob Copy says:

      So we only copy RFID fobs and cannot repair fobs. Have you contacted your condo’s property management?

  4. Sue baker says:

    I am at work early morning sinc returning to work i seem to be setting the alarm off on a regular basis. I have been told that i am using the fob incorrectly. The alarm system is a square box with lighted info box at top. I generally pass it over the first two words on left hand side & this generally works. But sometimes like this morning i had to ring manager of company,he told me to use a master key which i did & it still would not turn alarm off. What am i doing wrong?pls help

    1. Fob Copy says:

      I’m sorry to say we are just a fob copying company and can’t diagnose alarm system problems. Good luck!

  5. Caroline says:

    Hi! My company just bought a bunch of fobs (I believe off ebay) and only one has a batch and card number. The rest are all blank. ( They show up as having no batch or card number when we scan them). Is it possible to create a batch and card number?

    1. Fob Copy says:

      If they are writeable and you are using them all for the same thing, they can just be copied.
      Wed don’t know who would have a machine which can create a batch number, sorry.

  6. Gregory says:

    Can I reader control 2 doors that are only 5 feet apart? It is fine if they both open at the same time.

    1. Fob Copy says:

      Yes, that seems very possible.

  7. Daniel says:

    My Fob to the condo does not work, even after reprogramming. What can be the problem? What causes such malfunction? Can this be prevented?

    1. Fob Copy says:

      The fob itself could be faulty.

  8. James Glover says:

    If my building gave me a fob for access to the building, can I program the FOB reader on my door to use that same FOB? Do I need to get the landlord involved to make it work?

    1. Fob Copy says:

      This is presumably possible but we don’t know how to do it. It might be against your condo bylaws, as well.

Comments are closed.