NCCER Electronic Systems cheat sheet

Lockout/tagout (LOTO) requires isolating all energy sources-electrical, mechanical, pneumatic, hydraulic, stored-before servicing; verify zero energy state by test, not assumption.

OSHA 29 CFR 1910.147 governs LOTO for general industry; 1910.269 covers power generation/transmission/distribution work.

Arc flash boundary: the distance at which incident energy equals 1.2 cal/cm² (the threshold for second-degree burn); NFPA 70E sets PPE categories and arc-rated clothing requirements.

Approach boundaries (NFPA 70E): limited, restricted, and prohibited boundaries depend on nominal voltage; only qualified persons cross restricted boundaries with appropriate PPE.

Personal fall arrest systems: full-body harness, anchorage rated 5,000 lb per worker, and maximum free-fall distance of 6 ft before activation.

Confined space entry requires atmospheric testing (oxygen 19.5–23.5%, LEL <10%, H2S/CO within limits) before entry and continuous monitoring; permit-required spaces need an attendant.

GFCI protection is required on all 120 V, 15/20 A temporary receptacles on construction sites; test before each use.

Class C fires involve energized electrical equipment-use non-conductive extinguishing agents (CO2, clean agent); de-energize before using water-based agents.

Hazard communication (HazCom/GHS) requires Safety Data Sheets (SDS) for every hazardous chemical on site and labeled containers.

Ohm's Law: V = I × R; power: P = V × I = I²R = V²/R.

Series circuit: R_total = R1 + R2 + …; current is identical through all components; voltage divides proportionally to resistance.

Parallel circuit: 1/R_total = 1/R1 + 1/R2 + …; voltage is identical across branches; current divides inversely to resistance.

AC impedance Z combines resistance R and reactance X: Z = √(R² + X²); inductive reactance X_L = 2πfL, capacitive reactance X_C = 1/(2πfC).

Three-phase power: P = √3 × V_LL × I × PF for balanced loads; single-phase: P = V × I × PF.

Transformer turns ratio: V_primary/V_secondary = N_primary/N_secondary = I_secondary/I_primary.

American Wire Gauge (AWG): lower gauge number = larger conductor; every 3 AWG steps doubles cross-sectional area, every 6 steps halves resistance.

Voltage drop single-phase: V_drop = 2 × K × I × L / CM (K = 12.9 for copper, 21.2 for aluminum; CM = circular mils).

NEC Article 310 ampacity tables are based on 30 °C ambient and no more than three current-carrying conductors in a raceway; apply correction and adjustment factors otherwise.

NEC Chapter 7 (Articles 700–770) covers emergency, legally required, optional standby, fire alarm, and communications circuits; Article 800 covers communications circuits, 760 fire alarm, 725 Class 1/2/3 circuits.

NFPA 72 governs fire alarm installation, testing, and inspection; NFPA 70 (NEC) governs electrical installation; NFPA 101 Life Safety Code governs egress.

TIA-568 defines structured cabling performance categories (Cat 5e, 6, 6A, 8) and component/installation requirements; TIA-569 covers pathways and spaces; TIA-606 labeling.

On a drawing set, plan views show horizontal layout; riser diagrams show vertical distribution; single-line diagrams show power distribution hierarchy; schedules list device types, quantities, and circuit assignments.

Scale notation: 1/4" = 1'-0" means one-quarter inch on the drawing equals one foot in reality; convert drawing dimensions to actual using the scale factor before ordering material.

Title block contains project name, drawing number, revision, scale, and designer; revision clouds and delta triangles mark changes since the previous issue.

Detail and section callouts reference another sheet with a bubble (e.g., 3/A-501 = detail 3 on sheet A-501); confirm the referenced sheet is the current revision.

Symbols legend (keynote list) must be used before interpreting device symbols; symbols vary between disciplines and firms.

Coordinate systems: architectural drawings use feet-inches; site/civil drawings often use decimal feet with a benchmark elevation; verify units before layout.

Horizontal cabling maximum length: 90 m (295 ft) permanent link plus 10 m (33 ft) of patch cords = 100 m channel maximum.

Backbone cabling: fiber or copper between telecommunications rooms, equipment rooms, and entrance facilities; distance limits vary by media (e.g., 90 m for UTP backbone in-building).

TIA-568 separation from power: maintain minimum separation distances from unshielded power lines based on voltage and whether the power raceway is metallic or nonmetallic.

Bend radius: 4× cable diameter for UTP during installation, 10× for fiber (minimum); exceeding causes attenuation and return-loss failures.

Pull tension: 25 lbf (110 N) maximum for 4-pair UTP; fiber limits vary by manufacturer-consult the cable datasheet.

Cable support: horizontal cable supported at intervals not exceeding 5 ft (1.5 m); no more than 25 lbf of pulling tension on Cat 6.

Telecommunications room (TR) requires dedicated power, grounding/bonding to the telecommunications grounding busbar (TGB), environmental control, and clear working space per NEC 110.26.

Pathways: EMT, IMC, and rigid conduit are common; J-hooks support cable in ceilings; sleeves and firestopping are required where pathways penetrate fire-rated assemblies.

Testing: permanent link and channel tests report insertion loss, NEXT, PS-NEXT, return loss, and (for Cat 6A/8) alien crosstalk; results must meet the specified category.

Speaker impedance and amplifier matching: parallel connection of two 8 Ω speakers yields 4 Ω; series yields 16 Ω; total load must not fall below the amplifier's rated minimum impedance.

70 V/100 V distributed systems use transformers at each speaker; power taps determine wattage drawn, and total tap wattage must not exceed amplifier rating (with 20% headroom recommended).

Line level is nominally 0.775 V (-10 dBV consumer / +4 dBu pro); speaker level is several volts to tens of volts-never connect speaker outputs to line inputs.

HDMI versions: 1.4 supports 4K at 30 Hz; 2.0 supports 4K at 60 Hz; 2.1 supports 8K at 60 Hz and 4K at 120 Hz with higher bandwidth (48 Gbps).

HDCP 2.2/2.3 is required for 4K UHD protected content; a non-compliant splitter or display causes a blank screen or downscaling.

Projector throw ratio = throw distance ÷ screen width; use it to select lens and mounting location. Screen gain affects brightness; ambient light requires higher gain or higher-lumen projector.

Aspect ratios: 16:9 (1.78:1) for HDTV/UHD; 2.39:1 for widescreen cinema; letterboxing preserves original aspect; pillarboxing adds side bars.

Video bandwidth: bandwidth (Gbps) ≈ pixel clock × bits per pixel; 4K60 4:4:4 8-bit requires about 18 Gbps, exceeding HDMI 2.0's 18 Gbps limit at the margin-use 4:2:0 or HDMI 2.1.

Acoustic treatment: absorption controls reflections and reverberation; diffusion scatters sound; bass traps address low-frequency standing waves; place absorption at first reflection points.

Access control architecture: card reader → reader interface/controller → access control panel → head end (software); door hardware includes electric strike or maglock, REX (request-to-exit) sensor, and door position switch (DPS).

Fail-safe vs. fail-secure: fail-safe locks unlock on power loss (maglocks; required for egress paths); fail-secure locks remain locked on power loss (electric strikes on secure storage).

NFPA 101 requires free egress: electrified locks must release on fire alarm activation, and delayed egress (15 or 30 s) must comply with NFPA 101 and local code.

Wiegand is a legacy interface; OSDP (Open Supervised Device Protocol) is the modern standard, supporting encryption (Secure Channel) and bidirectional communication.

Card technologies: 125 kHz proximity (low frequency, unencrypted, cloneable), 13.56 MHz smart cards (MIFARE DESFire EV2/EV3, HID iCLASS Seos) support mutual authentication and encryption.

CCTV: IP cameras use PoE (802.3af ~15.4 W, 802.3at ~30 W, 802.3bt up to 90 W); analog uses coax with baluns; resolution measured in pixels; frame rate in fps; lens focal length determines field of view.

Camera coverage: identify (face recognition) requires ~80–100 px/ft; recognize ~40–50 px/ft; observe ~20 px/ft; monitor ~10 px/ft (DORI standard).

Intrusion detection: PIR detects changes in infrared energy (heat) and motion; dual-technology detectors combine PIR and microwave to reduce false alarms.

Storage calculation: GB = (bitrate Mbps × 3600 × hours × days) ÷ (8 × 1000); verify retention requirements before sizing.

NFPA 72 defines initiating devices (smoke, heat, pull stations), notification appliances (horns, strobes, speakers), and the fire alarm control unit (FACU).

Smoke detector spacing: 30 ft (9.1 m) maximum between detectors on smooth ceilings; 15 ft from walls; use 900 sq ft per detector as a general rule for smooth ceilings.

Heat detector spacing: 50 ft for fixed-temperature/rate-of-rise on smooth ceilings; 25 ft from walls.

Notification appliance circuits (NAC): strobes must be synchronized within an area; candela ratings per NFPA 72 (15, 30, 75, 110 cd) selected by room size and mounting height.

Class A wiring (Style D/6) survives a single open or ground fault; Class B (Style B/4) does not-Class A is required for many high-rise and life-safety applications.

Addressable systems use an SLC (Signaling Line Circuit) with individually addressed devices; conventional systems use zones and end-of-line (EOL) resistors.

Fire alarm control units require dedicated, unswitched power per NEC Article 760; battery backup must support 24 hours of standby plus 5 minutes of alarm (or 15 minutes for voice systems).

Inspection/testing per NFPA 72: smoke detectors annually, heat detectors annually, notification appliances annually, and system functional tests per the schedule in Table 14.4.3.2.

Interface to suppression: pre-action and deluge systems, clean agent (FM-200, Novec 1230), and kitchen hood suppression require cross-zoning and shutdown interlocks.

OSI model layers 1–7: Physical, Data Link, Network, Transport, Session, Presentation, Application; switches operate at Layer 2, routers at Layer 3.

Ethernet standards: 1000BASE-T over Cat 5e/6 up to 100 m; 10GBASE-T over Cat 6 up to 55 m or Cat 6A up to 100 m; 25/40/100GBASE over fiber or Cat 8 (30 m).

PoE standards: 802.3af (15.4 W at PSE, 12.95 W at PD), 802.3at/PoE+ (30 W/25.5 W), 802.3bt Type 3/4 (60/90 W).

IPv4 private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16; subnet mask /24 = 255.255.255.0 = 254 usable hosts.

VLANs segment broadcast domains; 802.1Q trunking tags frames; inter-VLAN routing requires a Layer 3 device.

Fiber: single-mode (OS1/OS2) for long distance (km); multimode (OM3/OM4/OM5) for shorter runs in buildings; connector types LC, SC, ST; polish UPC vs. APC.

Wireless: 802.11ax (Wi-Fi 6) operates 2.4/5 GHz; 6 GHz for Wi-Fi 6E; channels 1, 6, 11 are non-overlapping in 2.4 GHz (North America).

Cable testing: TIA-568 permanent link and channel tests; fiber uses OLTS (insertion loss) and OTDR (fault location).

Network documentation: as-built drawings, IP address plans, VLAN assignments, and port maps are required deliverables for commissioning.

Commissioning phases: pre-functional (static) checks, functional performance tests (FPT), integrated systems testing (IST), and owner acceptance/training.

Pre-functional checklist: verify power, grounding, terminations, labeling, firmware versions, and device addressing before energizing.

Functional test: each device and sequence of operation is exercised and documented with pass/fail and witness signature.

Integrated systems test: verify cross-system sequences-e.g., fire alarm activates door release, HVAC shutdown, elevator recall, and PA override.

Point-to-point verification: confirm every input and output in the control system matches the as-built and the sequence of operations.

Test documentation: test scripts, results logs, punch lists, and a commissioning report; retain for the warranty period.

Acceptance testing per NFPA 72 requires a record of completion and a record of inspection and testing; the AHJ witnesses certain tests.

Network integration: BACnet (ASHRAE 135) for BAS, Modbus for legacy devices, LonWorks; verify protocol gateways and IP addressing before integration.

Retro-commissioning investigates existing systems; ongoing commissioning maintains performance over time.

Work breakdown structure (WBS) decomposes scope into deliverable-oriented tasks; the critical path is the longest sequence of dependent tasks and determines project duration.

Float (slack) = late start − early start; activities on the critical path have zero float.

Change order process: documented request → impact assessment (cost, schedule) → owner approval → revised contract documents; never proceed on verbal authorization.

RFI (Request for Information) clarifies ambiguous drawings/specs; submittals (shop drawings, product data, samples) require approval before fabrication/installation.

Contract types: lump sum (fixed price), time and materials (T&M), cost-plus; retainage is a percentage withheld until substantial completion.

Substantial completion triggers warranty start, owner occupancy, and release of retainage (per contract); punch list items remain.

Earned value: CV = EV − AC (positive = under budget); SV = EV − PV (positive = ahead of schedule); CPI = EV/AC; SPI = EV/PV.

Customer communication: document all decisions in writing, confirm scope in meeting minutes, and escalate issues early with options and recommendations.

Safety and quality: pre-task planning, job hazard analysis (JHA), and daily reports support both safety compliance and dispute resolution.