Access Control is the process of using electric locking devices controlled by a central, or sometimes local, intelligent device. It gives you the ability to schedule your doors, track who is entering and when they are entering.
Your Access Control system can lock and unlock your doors on a schedule, can allow your users to unlock your doors. Users can be scheduled as well. Your cleaning crew can be allowed access only between the hours of 5pm and 9pm on Monday, Wednesday and Friday, if that is their cleaning schedule.
There are several types of media that can be used to identify users. The most popular is proximity cards. Proximity cards come in many variations. The most common is the 26 bit wieghant card. The proximity card has an antenna in it that, when placed in close proximity to a receiver, emits a unique identification number or other string of information that is decoded and authorized by the system.
The next most used is the mag stripe cards. Mag stripes are like credit or debit cards with user information encoded on one of several tracks available on the card.
Least used but perhaps the most interesting is the various biometric devices:
Hand geometry scanners
These are not as widely used and many of these technologies still have less than perfect reliability rates and are used in conjunction with other media or PIN numbers.