The advantages and disadvantages of each are outlined below.

The proximity card contains a wire and a small memory chip. The electronic field around the reader always emits an energy field. When the card is passed close to the reader, the wire absorbs some of the energy and activates the card. The memory chip sends an activation number or code back to the reader for verification and access. Since power is obtained from the reader, the card does not need a battery. The main advantages of the proximity card are that it's more secure than magnetic stripes and it can be held close to the reader without actual physical contact or swiping. However, this comes with a price tag of about $5.00 to $6.00 per card.

Proximity, bar coding and magnetic striping are often referred to as write once, read many times, since the information is embedded on the card and the card can be read many times.

A step up from this is the Smart Card which is considered as a write many times, read many times card. Essentially, it's an electronic memory system that can be re-written, similar to a floppy disc. The memory is far greater than both a bar code or magnetic stripe, allowing 8K or 8,000 bits of information compared to 26 to 52 bits on a mag stripe or proximity card.

This added storage capacity can be used for e-cash capabilities, where a certain amount can be programmed into the card and any purchases from cafeterias, vending machines or parking meters can be deducted from the amount on the card. Basically this allows one card to serve as a photo ID card, access control card and portable, electronic "wallet". For this reason many universities and colleges are now adopting smart cards to serve as an all-in-one solution on campus. The one card can also be used for the library and computer access. Previously, smart cards were comparatively expensive but now that they have dropped in prices, they are gaining more widespread use.

There is another type of Smart Card. This type of card is used mostly for pre-paid calling and cannot be re-written or re-loaded. It uses a system similar to fuses. Once the fuse is burnt out it cannot be used again. Combine many of these electronic fuses on a card and a card reader can short circuit a fuse for each penny of long distance calls you make. Since the card cannot be re-used, you must buy a new card rather than having it loaded with a new value. This type of card could be used for access to a commercial venture such as an amusement park or car wash, allowing access several times only. However, it is not generally practical for business or government applications.

Smart Cards have the added advantage of being able to perform simple processing on the card itself for e-cash and other purposes.

Proximity, bar coding and magnetic striping provide an identification number or code when a card is swiped or activated. Codes or numbers can be customized to identify the office site, facility, department and ID number or any other combination of information. Once the code is read, the access control system either allows or denies entry. This allows you to change access parameters to a particular person at any time. Or, if a disgruntled employee leaves with a card, all access can be denied. The same can be done with a smart card, but the added memory and processing power allows a multitude of other uses such as e-cash.

Whatever you choose, consider the security and cost of the cards as well as other features you might need such as e-cash capabilities.