Delaware Low Voltage Practice key terms

The fixed relationship among voltage, current, and resistance in a circuit, stated as voltage equals current times resistance. Knowing any two values lets you calculate the third for troubleshooting and conductor sizing.

The relationship describing electrical power in watts as voltage multiplied by current in a resistive circuit, with variants using resistance. Used to size circuits, transformers, and power supplies for low voltage equipment.

The loss of voltage along a conductor caused by its resistance, proportional to current, conductor length, and conductor gauge. Excessive drop causes equipment malfunction, so low voltage runs often use larger wire or shorter distances.

American Wire Gauge, the standard numbering system for conductor size. Lower numbers indicate larger conductors, and each three-step change roughly doubles or halves cross-sectional area and current capacity.

Electrical current that reverses direction periodically, typically 60 hertz in North American buildings. Most premises power is AC, while many low voltage and data signals are direct current or high-frequency waveforms.

Electrical current flowing in one constant direction, supplied by batteries, power supplies, and rectifiers. Access control, CCTV, and many control systems operate on low voltage DC.

The total opposition a circuit presents to alternating current, combining resistance, inductive reactance, and capacitive reactance. It matters for data cabling, audio distribution, and signal integrity at higher frequencies.

The inherent impedance of a transmission line or cable, such as 100 ohms for twisted pair data cable, determined by its construction. Mismatches between cable and equipment cause signal reflections and data errors.

Unwanted signal coupling from one conductor or pair into another within the same cable or bundle. It degrades data performance and is reduced by twisting, shielding, and proper pair separation.

A cabling method where two conductors carry equal and opposite signals so noise couples equally and cancels at the receiver. Twisting maintains balance and supports high-speed data transmission.

Cable containing insulated conductor pairs twisted together without an overall shield, the most common voice and data cabling. It relies on twisting and balance rather than shielding to reject interference.

Twisted pair cable with a metallic foil or braid barrier around pairs or the whole cable to reduce electromagnetic interference. Shields must be properly terminated and grounded to be effective.

Cable with jacket and insulation rated for use in air-handling spaces, producing limited smoke and flame spread. Building codes require it when cable runs through return-air ceilings without conduit.

Cable rated for installation in vertical shafts between floors, offering flame propagation resistance suited to that environment. It is commonly designated by a specific listing mark distinguishing it from plenum and general-purpose cable.

A rigid metal or nonmetallic support system that carries cables across open spans and routes them neatly. It requires appropriate fill, support spacing, and bonding of metal sections.

An enclosed channel such as conduit or tubing designed to hold and protect wires and cables. It provides physical protection and may serve as an equipment grounding path when metallic and properly bonded.

A circuit supplied by a listed power source limited in voltage and energy so it presents low fire and shock risk. Communications, signaling, and control wiring commonly falls under Class 2 rules.

A circuit with higher permitted voltage and energy than Class 2 but still limited, often used for signaling and control. Its wiring rules differ on separation from power conductors and permitted cable types.

A circuit whose source limits available current and power under fault conditions, reducing fire and shock hazards. Such circuits have relaxed installation requirements compared with general power wiring.

The National Electrical Code article governing communications circuits, covering installation, cable types, and separation from power conductors. It applies to telephone, data, and similar signal wiring in buildings.

The National Electrical Code article covering Class 1, Class 2, and Class 3 remote-control, signaling, and power-limited circuits. It establishes wiring methods and separation rules for control and low-energy systems.

The National Electrical Code article addressing fire alarm systems, including circuit classifications, wiring methods, and installation requirements. It distinguishes power-limited from non-power-limited fire alarm circuits.

The National Fire Alarm and Signaling Code, which sets installation, performance, testing, and maintenance requirements for fire detection and notification systems. It works alongside electrical code articles on fire alarm wiring.

The wiring loop connecting detectors and manual pull stations to the fire alarm control panel. It is monitored so opens, shorts, or ground faults are reported as trouble conditions.

The circuit powering audible and visible warning devices such as horns, speakers, and strobes. Design must account for voltage drop so all devices operate within their listed voltage range.

Continuous monitoring of a circuit or device so that faults such as opens, shorts, or loss of power are detected and annunciated. Supervised circuits are required for reliable life safety operation.

A fire alarm architecture in which each device has a unique identifier, letting the panel report its exact location and status. It simplifies troubleshooting and speeds emergency response compared with conventional zones.

An unintended connection between a conductor and earth or grounded metal, allowing current to flow outside its normal path. It can trip protective devices, cause shock hazards, or create fire alarm trouble signals.

The conductive element, such as a rod or metal water pipe, that establishes a direct connection to earth. It anchors the grounding system and helps stabilize voltage during faults and surges.

The intentional connection of metal parts to form an electrically continuous path that equalizes potential. It prevents dangerous voltage differences between equipment, raceways, and grounding conductors.

A component that limits transient overvoltages by diverting excess energy to ground, protecting sensitive electronics. It is installed at service entrances or near equipment being safeguarded.

Power over Ethernet, a technology delivering both data and DC power over twisted pair cabling to devices such as cameras and access points. Power budgets and cable length limits must be respected in design.

A standardized hierarchical cabling architecture with defined subsystems, media, and connectors supporting voice, data, and video. It enables flexibility, documentation, and consistent testing of building networks.

A passive termination block where horizontal cabling is terminated and cross-connected to network equipment. It organizes circuits, simplifies moves and changes, and supports testing and labeling.

An electronic system that regulates entry through doors using credentials such as cards, keypads, or biometrics. It includes readers, controllers, locks, and fail-safe or fail-secure power arrangements.

A lock that unlocks when power is removed, allowing free egress during emergencies such as fire. It is typically required where life safety codes govern egress doors.

A lock that remains locked when power is lost, maintaining security during outages. It is used where egress is provided by other means and security is the priority.

A device such as a push button or motion sensor that signals the controller to release a door lock for egress. It is a key element of code-compliant access-controlled doors.

A closed-circuit television arrangement of cameras, lenses, and recording equipment used for surveillance. Modern systems often use IP cameras and network video recorders.

A Delaware credential authorizing a person or business to install, alter, or maintain low voltage wiring and related systems under the state's licensing rules. It establishes scope of work and accountability.

An official authorization issued by a local authority before regulated electrical or low voltage work begins. It allows inspection of the installation for code compliance and is often required for new or altered systems.

A review by an authority having jurisdiction of completed or in-progress work to verify code compliance. Passing inspection is typically required before systems are energized or concealed.

The organization, office, or individual responsible for enforcing code requirements and approving equipment and installations. In Delaware, local building officials and state agencies may fill this role.