WBCHSE HS Vocational Telecom key terms

The rule stating that current through a conductor equals the voltage across it divided by its resistance, written I = V/R, used to calculate any one of the three quantities when the other two are known.

The rate at which electric charge flows past a point in a circuit, measured in amperes. One ampere means one coulomb of charge passing each second.

The electrical potential difference between two points that pushes charge around a circuit, measured in volts. It is the driving force that makes current flow through a conductor.

The opposition a material offers to the flow of electric current, measured in ohms. It depends on the material, its length, its cross-sectional area and its temperature.

A two-terminal component made to provide a known resistance in a circuit, used to limit current, divide voltage or set bias. Its value is marked by a colour code.

A component that stores electric charge between two conducting plates separated by an insulator, measured in farads. It blocks direct current while allowing alternating current to pass.

A coil of wire that stores energy in a magnetic field when current flows through it, measured in henries. It opposes changes in current and is basic to transformers and filters.

A two-terminal device made of p-type and n-type material that conducts easily in one direction and blocks the other, used for rectification, protection and clamping in power supplies.

A three-terminal semiconductor device that can amplify a signal or act as an electronic switch. Bipolar and field-effect types are the building blocks of amplifiers and logic circuits.

A circuit, usually built from diodes, that converts alternating current into pulsating direct current. A filter capacitor then smooths the output for use by electronic equipment.

Equipment that converts mains alternating current into the stable direct current voltages needed by telecom circuits, typically using a transformer, rectifier, filter and regulator.

A rechargeable battery bank connected to telecom equipment so service continues during mains failure. Lead-acid or lithium cells are kept charged by a rectifier and switched in automatically.

A logarithmic unit used to express the ratio of two power or voltage levels. In telecom it measures gain, loss and signal strength along a transmission path.

The reduction in signal strength as it travels along a cable, fibre or radio path, usually expressed in decibels per kilometre. It grows with distance and frequency.

The range of frequencies a channel can carry, measured in hertz, or the maximum data rate a link supports. Wider bandwidth allows more information to pass per second.

The process of varying a carrier wave's amplitude, frequency or phase in step with an information signal so it can be transmitted efficiently over a medium.

The reverse of modulation: recovering the original information signal from a received modulated carrier. It is performed by the receiver or modem front end.

A continuous high-frequency wave that is modulated by an information signal and then transmitted. Its frequency is chosen to suit the medium and the licence band.

The ratio of useful signal power to unwanted noise power at a point in a system, usually in decibels. A higher ratio means clearer reception and fewer transmission errors.

Any unwanted electrical disturbance that adds to a wanted signal, arising from thermal motion, interference or equipment faults. Excessive noise corrupts data and degrades voice quality.

A cable in which two insulated copper conductors are twisted together to reduce interference and crosstalk. It is widely used for telephone lines and LAN connections.

A cable with a central copper conductor surrounded by insulation, a braided metallic shield and an outer jacket. The shield confines the signal and reduces interference.

A thin glass or plastic strand that guides light along its length by total internal reflection, carrying very high data rates with low loss and immunity to electrical interference.

The complete reflection of light back into a denser medium when it strikes the boundary with a less dense medium beyond the critical angle. It is the guiding mechanism in optical fibre.

A number describing the light-gathering ability of an optical fibre, derived from the refractive indices of core and cladding. It sets the acceptance cone for launched light.

Unwanted transfer of a signal from one conductor or channel into a neighbouring one, heard as faint speech or hiss. Twisting, shielding and spacing reduce it.

The impedance a transmission line presents to a travelling wave, determined by its geometry and materials, typically 50, 75 or 120 ohms. Mismatches cause reflections and loss.

Adjusting the impedance of a source, line and load so they are equal, maximising power transfer and preventing signal reflections at joints and terminations.

The subscriber's set containing a microphone, earpiece, dialling keypad and ringer, which converts sound to electrical signals and back and signals the exchange.

The pair of copper wires connecting a subscriber's premises to the nearest exchange, carrying speech, dialling signals and ringing current. Also called the subscriber line.

A continuous tone sent by the exchange to a subscriber whose instrument has gone off-hook, confirming that the exchange is ready to receive dialled digits.

A building and switching system where subscriber lines meet and calls are connected to other subscribers or trunk routes. It provides battery, ringing and supervisory functions.

The process of setting up, maintaining and releasing a temporary path between two subscribers or circuits through a network node, so many users can share common transmission facilities.

A high-capacity transmission link between two exchanges or network nodes that carries many calls at once, shared dynamically rather than dedicated to one subscriber.

The small geographical area served by one base station in a mobile network. Neighbouring cells use different frequency groups so spectrum can be reused across the service area.

The automatic transfer of an active call or data session from one cell or base station to another as the user moves, performed without dropping the connection.

The radio equipment and antennas at a cell site that communicate with mobile handsets and link them to the network controller and core network.

A device that modulates digital data onto a carrier for transmission and demodulates incoming signals back to data, enabling computers to communicate over telephone or cable links.

A network device that forwards data packets between different networks by examining destination addresses and choosing the best available path.

A networking device that connects devices within one local network and forwards frames only to the port where the destination device is attached, reducing unnecessary traffic.

A unique numeric label assigned to a device on an internet protocol network, used to route packets to the correct destination. IPv4 uses 32 bits; IPv6 uses 128.

A 32-bit number that separates the network portion of an IPv4 address from the host portion, telling a device which addresses are local and which must be routed.

A 48-bit hardware address burned into a network interface card, used by switches to forward frames within a local area network.

A test instrument that sends light pulses into a fibre and measures reflected power to locate breaks, splices and connectors and to estimate loss along the link.

A permanent joint made between two optical fibres, usually by fusion arc welding, to create a low-loss continuous path. Splice loss is measured during link testing.

Connecting exposed metalwork and equipment frames to the ground through a low-resistance path so fault currents flow safely away and protection devices operate.

Items worn by a worker to reduce injury risk, such as helmets, safety shoes, gloves, goggles and harnesses. It supplements, but never replaces, safe working practice.

The physiological effect of current passing through the body, which can cause burns, muscle contraction, breathing arrest or heart fibrillation. Switching off and isolating the supply prevents it.

A person who identifies a business opportunity, gathers resources, takes financial risk and organises a venture to deliver a product or service to customers.

A written document describing a venture's product, target market, operations, costs, funding needs and expected returns, used to guide the owner and persuade lenders or investors.

The sales volume or revenue at which total income exactly equals total cost, so the business makes neither profit nor loss. It helps set prices and sales targets.

The support and assistance given to customers before, during and after a purchase, including listening to complaints, explaining options and resolving faults promptly and politely.

Concentrating fully on a speaker, noting both content and feeling, then confirming understanding by summarising or questioning before responding. It reduces misunderstanding in customer and workplace conversations.

A formal contract between a service provider and a customer that states the expected quality of service, such as fault repair times and availability targets, with penalties for misses.

Scheduled inspection, cleaning, testing and adjustment of equipment carried out before faults occur, to reduce breakdowns, extend equipment life and keep service reliable.

A handheld test instrument that measures voltage, current and resistance, and often continuity. It is the basic tool for checking telecom power supplies and circuits.