The answer to this question is both simple and complex. At its most basic, an access control system is one that restricts physical access through a door or area. These systems come in many forms, but one of the most common is the use of a card reader to allow the card carrier to gain access. However, there are many ways to use these systems, including biometrics, such as those that utilize fingerprints or even iris scanning as identification, or RFID , which is radio frequency.
In addition, some of these systems can work with a whole network of access points, where you can gain access to a building with one key, or restrict activity only to certain areas. Most of these systems allow for what is called administrative rights, which is where one person programs and controls the access to a given area. The administrator can usually change and update this from day to day, or even from hour to hour if need be, and depending on the complexity of the security system. You can often incorporate these types of systems into other security devices, such as surveillance cameras and may be able to create one unit of security even with many kinds of devices and access points.
When choosing among your many options for a security system of this nature, it is very important that you consider how many people will be using this system, how secure it really needs to be and whether you will have open or restricted access within the building itself. For example, high security businesses may have a single access point at the main door where all employees can come in if they have a card. However, within the building, you can opt for additional security checkpoints where more restriction is advisable and so can keep complete control over access within all perimeters in a building.
Consider the cost of hiring multiple security guards to control access at an entry point. Not only does it cost more, but it also has the possibility of human error; not so with electronic access. With the access control systems, you don't need a human to stand guard and possibly make mistakes but can let the electronics weed out those that don't belong without interference from people.
Remember that there is also a password or PIN-based option for many of these access control systems that make it much harder to bypass the security. People may share their cards with each other, or even steal them from one another, which essentially defeats the whole point, but with out the right password at a PIN number access points, it is much harder to get into a spot where you don't belong. This makes these types of access points excellent within the building where there are restricted areas.
However, with biometrics, it is very, very difficult to get in without truly belonging there. These kinds of modern and spy-worthy devices actually read your fingerprints, match them up and then unlock the door, so without your personal fingerprint, you cannot get in. This means that it is extremely difficult to sneak into a restricted area. These biometrics are usually exceptionally accurate and really, not that much more expensive than your basic card readers, and yet their sterling security makes them more than worth it for many people.
Today's computer technology has created unprecedented methods for security in an office or home, and you can easily find ways to either upgrade your current system to a computer controlled access system or can install one from scratch.