Application of Physical Security Systems
Design logic
Physical security systems should support a layered sequence: deter, detect, delay, respond. Deterrence may influence an adversary, but it is not a guarantee. Detection identifies an event; delay buys response time; response must be planned and resourced. Defense in depth means no single layer is trusted alone. CPTED concepts-natural surveillance, access control, territorial reinforcement, maintenance-support but do not replace engineered systems.
System families
Know perimeter systems (barriers, fencing, lighting, sensors), intrusion detection (interior/exterior sensors, alarm processing), access control (credentials, readers, controllers, locks, egress), video surveillance (cameras, recording, analytics, alarm assessment), and communications. Integration matters: an alarm without assessment and response is noise. Set performance expectations for detection probability, nuisance-alarm rate, video image quality, and door-held-open timing.
Traps
A common trap is treating cameras as prevention. Another is mixing fail-safe and fail-secure: fail-safe unlocks on power loss for life safety egress; fail-secure locks to protect assets, but egress must still comply with life-safety requirements. Do not ignore alarm assessment, operator workload, or cybersecurity of networked systems. Lighting supports detection and surveillance; it is not merely decorative deterrence.
Worked example
For a controlled exterior door, specify fail-secure locking for asset protection, but provide fail-safe egress hardware and a documented emergency release. Test alarm annunciation, video assessment, and response time.
Rule of thumb
Design from the required response, not from the product catalog. If detection cannot be assessed and answered, add assessment or reconsider the design.