10.4 Primary/Backup Power and Copper, Fiber & Wireless Transmission

Power is a countermeasure with a stopwatch

Primary and backup power sources in Domain 2 include grid, battery, UPS, generators, and alternative/renewable supplies. The exam is not asking you to memorize a generator catalog. It is asking whether the access panel, the locks, the cameras, the SOC consoles, and the mass-notification amplifiers still do the job you claimed when the utility feed dies at 01:14.

Grid / utility is the normal primary source. Design as if it will fail: weather, a backhoe, a building electrical outage that is not a regional blackout. Document which security loads are on emergency panels versus ordinary receptacles. A recorder on a “convenient” office outlet is not on the security power system.

Batteries on 12/24 V panels (intrusion, access control, fire-related power supplies) provide standby after the charger loses AC. Capacity is amp-hours. Usable capacity is less than the label after temperature, age, and cutoff voltage. Four-hour standby is a common security conversation; fire-alarm standbys are often longer because their codes say so. Do not copy a fire number onto a camera VLAN without reading the requirement that actually applies.

An uninterruptible power supply (UPS) rides through brief losses, conditions power, and gives orderly shutdown or generator overlap for 120/208 VAC loads: PoE switches, NVRs, workstations, IP amplifiers. Online double-conversion UPS units isolate the load better than small standby “battery bricks.” Runtime is watt-hours divided by load watts, not the VA number on the front sticker.

Generators (diesel or natural gas) with an automatic transfer switch cover long outages. They need fuel, weekly or monthly tests under load, ventilation, and a maintenance contract. A generator that never ran in test will not become reliable during a hurricane. Some sites use generators for life safety and leave security cameras off that bus—know that split and either accept dark video or fund the connection.

Alternative and renewable sources—solar with charge controllers, small wind, fuel cells—appear at remote gates, trailers, and sites with no utility. They are rarely the sole source for a hospital SOC. Size them for worst-month sun, not a marketing brochure, and still provide battery autonomy for nights and storms.

Worked example: panel, cameras, and locks do not share a runtime

A designer says “the system has four-hour backup.” Separate the buses.

24 VDC panel battery (access/intrusion standby)

Battery: two 12 V, 8 Ah batteries in series → 24 V, 8 Ah. Derate 20 percent for age and temperature → 6.4 Ah usable. Runtime = 6.4 Ah / 1.25 A = 5.1 hours.

If four 24 V magnetic locks remain energized on that bus at 0.25 A each, add 1.0 A. New total 2.25 A. Runtime = 6.4 / 2.25 = 2.8 hours, and the doors stay locked while occupants may need to leave—see the life-safety trap below.

120 VAC UPS for video (separate path)

A small online UPS with about 120 Wh of usable energy at this load: 120 Wh / 176 W = 0.68 hours ≈ 41 minutes. The panel can still be alive when every camera is dark. Quoting “four-hour backup” without this split is how a design narrative fails both the owner and a PSP item.

The bar chart below is the watt picture that makes the mismatch obvious: video and recording dominate AC watts, while the panel’s DC standby is modest until you leave maglocks holding.

Surge protection belongs on copper coming from outdoors and on AC feeds; a UPS is not a lightning arrester.

Trap: maglocks on UPS with no fire-interface discussion

Electromagnetic locks are typically fail-safe: loss of power unlocks the door. That is a life-safety feature for egress, discussed in building and fire codes (IBC means of egress and NFPA 101 concepts: listed hardware, request-to-exit, fire-alarm release, signage, delayed-egress listings where used). If you place maglock power on a UPS so the door “stays secure during a blackout,” you may have defeated the unlock-on-power-loss path unless a fire-alarm or emergency-release contact still drops the lock circuit independently of the UPS output. The lock must also release on fire alarm when utility power is present. Pair this with request-to-exit sensors and a visible release. Fail-secure electric strikes behave differently (they stay locked on power loss and are used where egress is through a mechanical lever). Do not copy maglock UPS logic onto every opening. Cross-reference the life-safety and locking chapter of this guide whenever a PSP item combines backup power with electrically locked egress doors. Security goals do not outrank the ability to get out of the building.

Copper, fiber, and wireless transmission

Signal and data transmission methods are copper, fiber, and wireless. Choose them for distance, interference, surge, bandwidth, and how the path fails—not for installer habit.

Copper includes twisted-pair Ethernet (generally 100 meters for typical Cat5e/Cat6 horizontal runs), analog coaxial video (hundreds of feet with quality loss and ground loops), and RS-485 for many access-control buses (on the order of 4,000 feet with correct cable and topology). Copper is easy to terminate and easy to damage. Outdoor copper is an antenna for surge and lightning; specify protectors bonded to a real ground. It also couples electromagnetic interference from elevators, radios, and variable-frequency drives—exactly the noise that makes analog video snowy and data retry. Do not run security copper in the same unshielded bundle as high-voltage feeders and then blame the camera brand.

Fiber optic cable carries light. It is immune to electromagnetic interference, electrically isolating buildings (no ground loop between two services), and it supports long runs: multi-mode commonly to hundreds of meters or a couple of kilometers depending on optics; single-mode to tens of kilometers. Bandwidth for many-camera backbones is the usual reason to go fiber between IDFs. It is harder to tap without detection than a casual copper tap, but it is not magic: protect the physical path, respect bend radius, and budget media converters or SFP ports. Fiber does not carry PoE; you still need power at the camera or a local injector.

Wireless includes unlicensed 2.4 / 5 / 6 GHz links, licensed microwave, and cellular. Licensing (for example FCC Part 15 unlicensed versus licensed microwave) decides whether you share spectrum with every office access point or have a coordinated frequency. Encryption (modern WPA3-Enterprise or equivalent AES on radios, management that is not a default password) is mandatory for security video and access events over radio; an open bridge is a broadcast. Rain fade grows with frequency and path length—5 GHz outdoor bridges are less rain-sensitive than 23 GHz or E-band backhaul; link budgets need fade margin, not just sunny-day RSSI. Jamming and interference are threats to detect (loss of heartbeat, sudden noise floor, failover to copper or cellular), not techniques to practice. Building penetration, Fresnel-zone clearance, and mounting in wind are physical-security site work. Point antennas so the path is clear; do not treat “more power” as a substitute for a blocked first Fresnel zone.

Transmission and power meet at the edge device: a wireless camera still needs local power; a fiber camera still needs a PoE injector or DC supply; a copper camera on a 41-minute UPS is not “four-hour video.” Specify the pair together.

If you carry one design sentence into the exam, carry this: calculate runtime per bus, release maglocks for egress even when the UPS is healthy, and pick copper, fiber, or wireless for the failure you cannot afford.