Access Control is unlocking a door or doors without the use of a key. Some ways to unlock doors are:
A code on a keypad
A card at a card reader
A button on a radio transmitter
A thumb print reader
Remotely from the Internet
Remotely from a telephone
Other things can be unlocked of controlled, such as:
What are advantages of Access Control ?
1) Many people can have access without giving out a lot of keys. 2) No costly re-keying ever needed. 3) History of who entered is available through an audit trail. 5) Limiting which door(s) or when the door(s) are available, and by whom.