Card readers and keypads are the essential element of things like electronic access control and security systems. These days, the credentials we refer to as "cards" may come in a variety of shapes and sizes which do not resemble cards all.
Biometrics, another rapidly evolving technology, doesn't even use a credential, but instead uses body parts and unique human characteristics.
The factor which differentiates "cards" from "keys" is that credentials do not use physical cuts or notches or keyways, although there are a number of hybrid products which combine certain qualities of mechanical keys with electronics to provide unique access control solutions.
Although it is recognized that electronic credentials and keypads will eventually supplant mechanical keys; it is unlikely that keys will ever phase out completely.
The three factors which will determine the fate of any technology are: Cost, Ease of Use and Level of Security Provided.
By cost, we mean the cost of the card, key or credential; the cost of the reader or lock cylinder or 'sensor'; and the cost to maintain the system, such as rekeying costs and maintenance required.
Ease of Use includes issues such as the familiarity of the device to the end-user; how reliably the system performs and how suitable the system is for a particular application.
Level of Security is how secure the device is against circumvention, either by physical attack or counterfeiting.
To locksmiths, it is obvious that due to the infinite variables, there can never be a single ideal solution for all situations, and therefore the ability to provide a variety of solutions is vital to the longevity of the locksmith's productive career.
Many card technologies are currently in use, depending on the application and the geographic location. Extensive 'legacy' systems are currently in use, and the trend is to transition them rather than suddenly halt their use because of the expense and inconvenience sudden switchovers incur.
Hollerith: A legacy technology which uses punched holes in plastic cards. This technology is still used on some hospitality (hotel) systems.
Barrium Ferrite: This technology uses magnetic material sandwiched between two layers of PVC material. This a legacy technology still used in parking entry control systems.
Mag Stripe: Uses a magnetic strip attached to a card. This is widely used for financial transactions and access control even though the technology is easily counterfeited and the readers are comparatively high maintenance. Large populations of magstrip cards are in use for debit/credit cards and student IDs.
A big advantage of magstripe is also its Achilles heel. Magstripe cards can be encoded in the field by the issuing agency or anyone else who can get their hands on a magstripe encoder/decoder. Get a hold of a credit card long enough to run it through an encoder, and you can recreate the card at will. Magstripe encoding schemes are relatively easy to figure out if they are not already in the public domain.
Wiegand: Uses small pieces of wire embedded between layers of PVC. They are difficult to counterfeit, but also expensive to manufacture. Additionally, Wiegand cards must be ordered pre-encoded, and therefore cataloging, warehousing and distributing Wiegand cards is more involved, and lead times to obtain additional cards can be problematic.
Optical & Infrared: Includes credentials encoded with barcodes or proprietary masks, either on the surface of the card or embedded between layers of PVC. Visible or invisible (Infrared) light sources inside the reader pass through the card and are picked up by a sensor. Bar code is ubiquitous in a variety of industries, but its value as a security protocol is questionable at best.
Proximity: This technology is the most widely used technology in access control applications. Proximity Cards have antennas and an integrated circuit embedded in each card which is powered by electromagnetic fields generated by the proximity reader. Proximity technology characteristically operates on a 125 kHZ frequency carrier.