ABSTRACT
The objective of physical access control is not to restrict access but to control it. That is, the data center
manager should know who is granted access, when access is granted, and why. This chapter provides
overview of the function of access control systems, the physical elements they can use, and the basic
techniques they employ. It also describes two popular access control technologies, keypad access control
and portable-key access control, and discusses their advantages and disadvantages. The chapter also
examines two other technologies, proximity access control and physical-attribute access control, as well
as several developing technologies.