Before you start investigating access control systems, sit down and determine the purpose the security system will serve. The most basic role of an access control system is to keep out anyone who’s not supposed to enter an area. This can be the front door, a parking garage, a server room, a personnel records room, or any other sensitive area.

All computerized access control systems keep records of when doors where opened and by whom. However, you may want one that functions as part of a time tracking system, to automatically punch workers in and out for payroll purposes. The system will still only grant access to authorized users, but the focus is more on time tracking than on having airtight security. For this application, you'll need an access control system that is compatible with your time and attendance software. If your staff is mostly salaried, this component won't be nearly as important.

Another point to consider: how secure do you need the system to be? A basic system usually features a keypad or swipe card. Higher security applications may require multiple means of authentication (a card and thumbprint, for example) and include more redundancy. They're also more expensive.

Finally, consider what other systems need to connect to your access control system. Monitored alarm systems and CCTV systems are two good examples. Make sure you include any connectivity requirements in your initial conversations with access control vendors.

Sizing your system
Once you understand the basic role the access control system will serve, think about the number of doors you need to secure. Smaller installations may include just one: a server room with an electronic keypad lock is a common example of a very small access control system. Remember that not every door has to have access control — you can simply leave some locked and only give keys to appropriate personnel.

If you plan ahead a little when purchasing your system, you’ll find it fairly easy to expand later. The smallest systems, designed for one or two doors, are not very expandable, but many four and eight door systems can be linked together when you need to expand. Once you know the number of doors you’ll be securing, gather information on each one: the physical makeup and use of your doors will impact the type of locks and entry systems you need. Are some doors for customers, and some only for employees? Are the doors wood, steel, or aluminum and glass? Are any designated as fire doors? Do you have any garage doors or parking lot gates to control?

Larger installations may include more than one site. An access control system that can be operated over a network lets you manage the security at all your locations from a central point.

Free exit and controlled exit systems
Another key distinction in access control systems is the difference between free exit and controlled exit systems. In a free exit system, there is no requirement for leaving a secure area. The system either detects someone approaching an exit (usually with motion sensors) and unlocks the door, or has a release button or bar that allows people to leave.

Controlled exit systems use the same security for travel in both directions: employees have to enter the code or wave their card to get in or out of the secure area. By law, access control systems have to be set up to allow people to exit if the system fails or power goes out. Controlled exit systems increase both security and your overall costs.