Editing Proximity card

{{Short description|Contactless smart card}}
[[Image:Proximity badge.km.jpg|thumb|250px|right|A passive proximity card for door access.]]
[[Image:Turnstile and MagLock Gate.jpg|thumb|250px|A proximity card controlled turnstile]]
[[Image:ProximityCard 1.jpg|thumb|250px|right|A passive proximity card with the plastic casing opened to show components: antenna coil and integrated circuit ''(black object bottom center)'']]
[[Image:ProximityCard 2.jpg|thumb|250px|right|Anatomy of proximity card: coil and IC]]
[[Image:Proximity card reader coil.jpg|thumb|250px|right|The proximity card coil of an electronic fare collection system]]

A '''proximity card''' or '''prox card'''<ref name="Reid">{{cite book   
  | last = Reid
  | first = Robert N. 
  | title = Facility manager's guide to security: protecting your assets
  | publisher = The Fairmont Press
  | date = 2005
  | pages = 144–146
  | url = https://books.google.com/books?id=rqFQdGnyXsYC&dq=proximity+card&pg=PA144
  | isbn = 0881734837}}</ref>  also known as a key card or keycard is a contactless [[smart card]] which can be read without inserting it into a reader device, as required by earlier [[magnetic stripe card]]s such as [[credit cards]] and contact type smart cards.<ref name="Norman">{{cite book   
  | last = Norman
  | first = Thomas L.
  | title = Electronic Access Control
  | publisher = Elsevier
  | date = 2011
  | pages = 57–58
  | url = https://books.google.com/books?id=TmRRTfAPfdYC&dq=proximity+card&pg=PA57
  | isbn = 978-0123820280}}</ref>  The proximity cards are part of the contactless card technologies. Held near an electronic reader for a moment they enable the identification of an encoded number.  The reader usually produces a beep or other sound to indicate the card has been read.

The term "proximity card" refers to the older 125&nbsp;kHz devices as distinct from the newer 13.56&nbsp;MHz [[contactless smartcard]]s.{{citation needed|date=October 2017}} Second generation prox cards are used for mass and distance reading applications. Proximity cards typically have a read range of up to {{cvt|50|cm|in}}<ref name="Reid" /> which is the main difference from the [[contactless smartcard]] with a range of {{cvt|2|to|10|cm|in|0}}. The card can often be left in a wallet or purse,<ref>Access Control Card Handling Guide
https://www.supercircuits.com/media/docs/proxcard_handling_guide_en.pdf  
</ref> and read by simply holding the wallet or purse near the reader. These early proximity cards can't  hold more data than a [[magnetic stripe card]], and only cards with smart chips (ie, [[contactless smartcard]]s) can hold other types of data like electronic funds balance for [[contactless payment]] systems, history data for time and attendance or biometric templates. When used without encoding data, only with the card serial number, contactless smartcards have similar functionalities to proximity cards.

== Types ==

=== Passive cards ===
Passive 125&nbsp;kHz cards, the more widely used type which were described above, are powered by [[radio frequency]] signals from the reader device and so have a limited range and must be held close to the reader unit.<ref name="Norman" /> They are used as [[keycard]]s for access control doors in office buildings. A version with more memory, [[contactless smartcard]]s, are used for other applications: [[library card]]s,  [[contactless payment]] systems, and [[public transit]] fare cards.

=== Active cards ===
Active 125&nbsp;kHz prox cards, sometimes called [[vicinity card]]s{{dubious|Active cards working on 125 kHz may not be called vicinity cards|date=December 2018}}, are powered by an internal lithium battery.  They can have a greater range, up to 2 meters (6&nbsp;ft). Other contactless technologies like UHF (Ultra High Frequency) smart cards  can reach up to 150 meters (500&nbsp;ft) and are often used for applications where the card is read inside a vehicle, such as security gates which open when a vehicle with the access card inside approaches, or [[automated toll collection]].<ref name="Norman" />  The battery eventually runs down, however, and the card must be replaced after 2 to 7 years.

== Method of operation ==
The card and the reader unit communicate with each other through 125&nbsp;kHz radio frequency fields (13.56&nbsp;MHz for the [[contactless smartcard]] cards) by a process called [[resonant inductive coupling|resonant energy transfer]].<ref name="Reid" /><ref name="Norman" />  Passive cards have three components which are sealed inside the plastic: an antenna consisting of a coil of wire, a [[capacitor]], and an [[integrated circuit]] (IC) which contains the user's ID number in specific formats and no other data.  The reader has its own antenna, which continuously transmits a short range radio frequency field.

When the card is placed within range of the reader, the antenna coil and capacitor, which form a [[tuned circuit]], absorb and store energy from the field, [[resonance|resonating]] at the frequency emitted by the reader. This energy is [[Rectifier|rectified]] to [[direct current]] which powers the [[integrated circuit]].  The chip sends its ID number or other data to the antenna coil, which transmits it by radio frequency signals back to the reader unit. The reader checks whether the ID number from the card is correct, and then performs whatever function it has been programmed to do for that ID number. All the energy to power the card comes from the reader unit, so passive cards must be close to a reader to transmit their data.

An active card contains a flat [[lithium cell]] in addition to the above components to power it. The integrated circuit contains a [[Receiver (radio)|receiver]] which uses the battery's power to [[amplifier|amplify]] the signal from the reader unit so it is stronger, allowing the card to detect the reader at a greater distance. The battery also powers a [[transmitter]] circuit in the chip which transmits a stronger return signal to cover the greater distance.

== Standards for proximity cards ==
Proximity cards are all proprietary. This is also the case of the memory-based first generation of [[contactless smartcard]]s. This means that there is no compatibility between the readers of a specific brand and the cards of another brand.

[[Contactless smartcard]]s are covered by the [[ISO/IEC 14443]] and/or the [[ISO/IEC 15693]] OR [[ISO/IEC 18000]] standards.  These standards define two types of card ("A" and "B", each with different [[communications protocols]]) which typically have a range up to {{cvt|10|cm|in|0}}. The related [[ISO/IEC 15693]] ([[vicinity card]]) standard typically works up to a longer range of {{convert|100|cm|in|0}}.
The reality is that [[ISO/IEC 14443]] as well as [[ISO/IEC 15693]] can only be fully implemented on microprocessor-based cards. The best way to check if a technology meets ISO standard is to ask the manufacturer if it can be emulated on other devices without any proprietary hardware.

== 125 kHz readers and formats ==
The card readers communicate in various protocols, for example the [[Wiegand protocol]] that consists of a data 0 and a data 1 circuit (or binary or simple on/off (digital) type circuit). Other known protocols are mono directional Clock and Data or bidirectional OSDP (RS 485), RS 232 or UART.  The earliest card formats were up to 64 bits long. As demand has increased, bit size has increased to continue to provide unique numbers. Often, the first several bits can be made identical; these are called facility or site codes. The idea is that company A has a facility code of ''xn'' and a card set of 0001 through 1000 and company B has a facility code of ''yn'' and a card set also of 0001 through 1000. For smartcards, a numbering system is internationally harmonized and allocated by Netherlands-based [[NEN (registration authority)]] according to [[ISO/IEC 6523]] and ISO/IEC 15459 standards.

==See also==

* [[Access badge]]
* [[Access control]]
* [[Campus card]]
* [[CharlieCard]]
* [[Common Access Card]]
* [[Credential]]
* [[Identity document]]
* [[Key (lock)#Keycard|Keycard]]
* [[Magnetic stripe card]]
* [[Near-field communication]]
* [[Photo identification]]
* [[Physical security]]
* [[Security]]
* [[Smart card]]
* [[Wiegand interface]]

==References==
{{Reflist}}

{{DEFAULTSORT:Proximity Card}}
[[Category:Contactless smart cards| ]]