This paper provides an introduction to the UFC 4-021-02 Electronic Security Systems Standard document prepared within the Unified Facilities Program of the U.S. Department of Defence, which is providing guidance to architects and engineers on how to plan and design electronic security systems for critical facilities and infrastructures. Then, this paper reviews the sensors, mainly the passive infrared-, seismic-, active infrared-, active ultrasonic-, microwave and fiber optic cable-sensors, that form the most frequently used sensors by an intrusion detection subsystem of electronic security systems for critical facilities and infrastructure protection. Lastly, this paper describes a generic perimeter electronic security system application with an unattended wireless sensor network (UWSN) and draws a conclusion by thoughts on other possible future sensor system developments.