Security, Access Control, and CCTV Systems
Security work blends code, power, and system design. Know access control fundamentals: readers, controllers, request-to-exit devices, door position switches, and the lock hardware types (fail-safe versus fail-secure). Fail-safe unlocks on power loss and is used where life safety requires egress; fail-secure locks on power loss and is used where security dominates. Free egress must always be maintained-no access control system may override the egress requirements of the building code.
CCTV topics include camera types, lens and field-of-view calculations, PoE power budgets, and cabling limits. Understand that PoE has per-port and total switch budgets, and that cable distance limits apply. Traps: specifying fail-secure on a required egress door, forgetting a request-to-exit device or mechanical release, and overloading a PoE switch. Also watch for privacy and recording-retention requirements.
Rule of thumb: egress wins-if a door is a required exit, the lock must release on fire alarm and on loss of power.
Worked example: a 16-camera PoE design. Sum camera draw, compare against the switch's total PoE budget, and reserve headroom; if over budget, add a midspan or a second switch rather than assuming all ports deliver full power.