The field guide.
Look up a component, follow a question, or discover where the systems meet.
100 entries to explore
Electricity generation
A generator or solar cell converts another form of energy into electrical energy. The grid connects that conversion to useful work elsewhere.
Transformers
Transformers make it practical to connect parts of an AC system that operate at different voltages.
Transmission networks
High-voltage connections let regions share generation, support one another, and move power over long distances.
Substations & protection
A substation is a controlled junction where power can be transformed, measured, connected, or safely disconnected by designed equipment.
Distribution networks
Local feeders, cables, and transformers connect the bulk electricity system to streets, buildings, and smaller generators.
Meters, power & energy
A meter records energy crossing a connection. Power tells you how quickly energy is being used at a particular moment.
The appliance & its circuit
A kettle, lamp, motor, or computer is a load: equipment that converts electrical energy into another useful form.
Balancing supply & demand
Electricity supply and use must remain closely matched while equipment, weather, and demand keep changing.
Energy storage
Storage takes in energy now and makes some of it available later, within both a power limit and an energy limit.
Solar panels & inverters
Photovoltaic cells produce DC electricity. An inverter makes that output usable by an AC installation and its connected grid.
Alternating & direct current
AC reverses polarity periodically; DC keeps one polarity. Conversion equipment connects the many places where both are useful.
Frequency & inertia
Frequency describes how often AC cycles repeat. Inertia and controlled responses influence how that rhythm changes after a disturbance.
Demand response
Flexible users can adjust consumption in response to an agreed signal, helping the system balance resources and manage peaks.
Microgrids & island operation
A microgrid coordinates local loads and resources and can be designed to operate independently of the wider grid.
Catchments & source water
A water supply begins with a landscape, an aquifer or another source whose condition shapes everything downstream.
Coagulation & clarification
Tiny suspended particles are gathered into larger clusters so that the plant can separate them from the water.
Filtration & membranes
A filter separates selected contaminants from a water stream, but its capabilities depend on its material and design.
Disinfection & monitoring
Disinfection inactivates susceptible microorganisms; monitoring checks that the wider treatment system is working.
Pumps & pressure zones
Pumps supply energy that helps water climb, overcome losses and reach the pressure needed within a supply zone.
Treated-water storage
A service reservoir or tank holds treated water so that production and demand do not have to match at every moment.
Distribution & the tap
Pipes, valves, service connections and building plumbing deliver treated water while preserving its quality.
Sewers & lift stations
A collection network carries used water from buildings toward treatment, using gravity where possible and pumps where needed.
Wastewater treatment
Physical and biological processes remove or transform pollutants before water is released or treated further for a particular reuse.
Sludge, digestion & biogas
Treatment concentrates some material into a solids stream that needs its own processing, safeguards and destination.
Discharge & water reuse
Treated water may return to the environment or serve another use, with requirements matched to that destination.
Metering & water losses
A water balance separates useful consumption, physical leaks and measurement errors so that the right problem can be addressed.
Water-quality sensing
Instruments and samples help operators recognise changes, investigate causes and verify that protective barriers are performing.
Desalination & concentrate
Desalination separates a less saline water stream from a saltier stream, adding a supply option with energy and environmental dependencies.
Stormwater & urban surfaces
The surface of a city changes how quickly rain runs off, what it carries and which drainage or treatment system receives it.
The browser
A browser coordinates requests, interprets documents, and turns received resources into the page you can see and use.
The access network
Wi-Fi, mobile radio, fibre, cable, and other links connect a device to the wider network through a service provider.
DNS & domain names
The Domain Name System lets applications look up information associated with names, including addresses used to contact services.
IP addresses & packets
Internet Protocol provides packet addressing that lets information cross networks built from different physical technologies.
Routers & forwarding
A router moves a packet between networks using its forwarding information and the packet’s destination.
Network interconnection
The internet works because independently operated networks agree to exchange traffic and communicate reachable destinations.
TCP, QUIC & reliable delivery
Transport protocols coordinate communication between endpoints, including ordering, loss recovery, and control of sending rates where required.
TLS & HTTPS
TLS helps endpoints establish an authenticated, encrypted connection, protecting application data while it travels between them.
Web servers & HTTP
HTTP gives browsers and services a common way to request resources and describe the resulting responses.
Caches & content delivery
A cache stores a reusable response so later requests may avoid repeating the full trip to its original source.
Optical fibre
Optical fibre guides light signals through glass, linking equipment across buildings, cities, and oceans.
Latency & round trips
Latency describes delay. It is different from throughput, which describes how much data is transferred over time.
Mobile access & handover
A mobile network coordinates a changing radio connection with transport links and core-network functions that provide data connectivity.
Congestion & packet queues
Packets wait when a link or device cannot serve arriving traffic immediately. Queue management and sender behaviour determine what happens next.
Station access
Entrances, lifts, wayfinding and information connect a railway to the people it serves.
Platforms and dwell time
The time spent stopped at a station can shape the capacity of an entire line.
The train
A train carries passengers while integrating propulsion, braking, doors, control and information.
Traction power
Substations and current collectors bring electrical energy from the grid to a moving train.
Train detection
Sensors turn the physical presence of a train into information a signalling system can use.
Signals and separation
Train control preserves enough protected space for movements to remain compatible.
Points and interlocking
Movable track selects the path; interlocking checks whether the proposed movement is compatible with other movements.
Track and support
Rails, fastenings, support layers and drainage keep the train’s path in the required position.
Braking and energy recovery
Braking reduces motion; regeneration can return some of that energy to a useful electrical destination.
Timetables and headway
A service plan coordinates trains, platforms, junctions, crews and maintenance opportunities.
Operations and recovery
Control teams coordinate the service when the railway’s actual state differs from the plan.
Depots and maintenance
A depot turns a fleet of vehicles into trains that are available, prepared and fit for their next duty.
Terminals and turnbacks
Reversing a train requires time and a compatible route, so the end of a line can limit the service along it.
Tunnel ventilation
Shafts, passages, fans and controls connect underground spaces to an environment that trains and people can use.
Drainage and flood resilience
Water routes, storage, pumps and inspections connect a railway to the surrounding catchment and its weather.
Switch on a kettle
Follow the change in demand from a familiar appliance back through the network and into the balancing process.
GUIDED JOURNEY · 7 MINFrom generation to appliance
Trace a conventional large-source supply path, then notice where real networks branch and vary.
GUIDED JOURNEY · 7 MINWhen evening demand rises
Explore the responses available when more electricity is needed, and why spare capacity is not the same as unlimited flexibility.
GUIDED JOURNEY · 7 MINFrom midday solar to evening light
A fictional building uses some midday solar immediately and stores some for later. Follow the boundaries that determine what is available after sunset.
GUIDED JOURNEY · 8 MINMove a load, change the peak
Follow a fictional charging load as an agreed schedule changes, and see why local limits and later demand still count.
GUIDED JOURNEY · 8 MINFill a glass of water
Follow one illustrative surface-water supply through complementary treatment barriers, storage and distribution. This route explains a common arrangement rather than promising that every city uses the same equipment.
GUIDED JOURNEY · 7 MINFollow water after the drain
Trace used household water through a sewered system. Watch the liquid and solids paths separate, then see why an outfall and a drinking-water supply are different destinations.
GUIDED JOURNEY · 8 MINWhen a water pump stops
Use a deliberately simplified reservoir to see how stored water can bridge a loss of inflow. Separate the inventory calculation from real pressure, water quality and emergency decisions.
GUIDED JOURNEY · 6 MINWhere does rain on a street go?
Follow rain across an imagined urban catchment. Compare separate storm drainage with a combined-sewer branch, and see why slowing water, treating it and protecting its destination are different tasks.
GUIDED JOURNEY · 9 MINFrom seawater to the tap
Trace an illustrative membrane-desalination supply, including pretreatment, permeate conditioning, concentrate management and delivery. The route explains functions without copying a particular plant’s design.
GUIDED JOURNEY · 10 MINLoad a page on your phone
Follow one ordinary HTTPS visit over Wi-Fi, from a typed address to a rendered page. Cached information and existing connections can shorten the real sequence.
GUIDED JOURNEY · 7 MINWhen a network path breaks
Trace how a missing link can change a route, why recovery takes time, and what the small interactive scenario leaves out.
GUIDED JOURNEY · 7 MINWhy the second visit can be faster
Explore how controlled reuse changes a web request, from cached naming information to a response stored near the reader.
GUIDED JOURNEY · 7 MINSend a photo while moving
Follow a fictional browser upload through mobile access, physical links, protected transport, and a receiving service.
GUIDED JOURNEY · 8 MINWhy a fast link can feel slow
Trace a fictional slow page through several distinct causes of delay without pretending that one speed number diagnoses them all.
GUIDED JOURNEY · 8 MINTake a train across the city
Trace a fictional journey between two stations on an electric urban railway. Every stage depends on more than the train itself.
GUIDED JOURNEY · 8 MINWhen a longer stop travels down the line
See why an extended station stop can be absorbed in one situation and propagate in another. This is a conceptual sequence, not a forecast for a particular incident.
GUIDED JOURNEY · 6 MINFollow a train’s energy
Trace energy through a simplified electric railway. Some energy can return during braking, but neither the train nor its power network is lossless.
GUIDED JOURNEY · 6 MINBefore the first passenger boards
A fictional morning service begins off the passenger map. Trace the links between a prepared vehicle, a planned path, power, route permissions and the platform where its public journey starts.
GUIDED JOURNEY · 8 MINAfter heavy rain, before normal service
An imagined downpour affects a low-lying section of an urban railway. Follow the reasons for disruption and recovery without treating the story as an operating procedure or forecast for a real line.
GUIDED JOURNEY · 8 MINOne morning, four systems
An original teaching journey through a fictional city with a treated-water network, electrically powered homes, internet access and an electric urban railway. All services are available this morning. Their connections are chosen to explain dependencies, not to describe every city or trace the same physical resources from end to end.
GUIDED JOURNEY · 9 MINOne interruption, different clocks
A fictional local electrical interruption affects a home router, a water pump and one railway traction section. We deliberately give other equipment different supplies or limited backup. These are chosen teaching assumptions, not predictions of outage duration, water pressure, safety or any real operator's response.
GUIDED JOURNEY · 9 MINWhen rain crosses the network map
A fictional storm sends runoff towards a low railway cutting and nearby infrastructure. The city has separate stormwater and wastewater networks, but unwanted rainwater can enter its sewers. The chosen locations and impacts are illustrative; no rainfall threshold, flood forecast or public safety decision is calculated.
GUIDED JOURNEY · 9 MINPower is back. What else must recover?
An original fictional recovery sequence after a local interruption. Equipment conditions and available support vary by service. The sequence is arranged for learning, not as an operating procedure or a universal restoration order; real decisions belong to the responsible operators and depend on the incident.
GUIDED JOURNEY · 9 MINHeadway
The time interval between successive trains at the same reference point. A planned headway describes the intended spacing; the achievable interval depends on the railway's limiting operating conditions.
ILLUSTRATED DEFINITIONDwell time
The time a train spends stopped at a station for the passenger exchange and associated departure activities. Its effect on following trains depends on the available margin and other constraints.
ILLUSTRATED DEFINITIONLatency
The time taken for data to travel between specified points. A measurement may describe one-way delay or a round trip; propagation, transmission, processing and waiting in queues can contribute.
ILLUSTRATED DEFINITIONBandwidth
In everyday networking language, the data-carrying capacity of a connection, usually expressed in bits per second. The precise meaning depends on the layer measured; useful application throughput can be lower.
ILLUSTRATED DEFINITIONPacket
A unit of data handled by a network protocol. An IP packet includes a header used for delivery and a payload; one application message may require many packets.
ILLUSTRATED DEFINITIONCapacity
The amount or rate a system can accommodate under stated conditions. Its units and limits depend on the service: stored volume, electrical output, data transfer and train throughput describe different capacities.
ILLUSTRATED DEFINITIONPower
The rate at which energy is transferred or converted. Electrical power is commonly measured in watts or kilowatts; one watt represents one joule of energy transferred each second.
ILLUSTRATED DEFINITIONEnergy
A quantity that can be stored, transferred or converted between forms. Electrical use is often measured in kilowatt-hours, combining the rate of power use with the duration of operation.
ILLUSTRATED DEFINITIONElectrical frequency
The number of cycles completed by an alternating electrical waveform each second, measured in hertz. Grid frequency is linked to the dynamic balance between electrical supply and demand.
ILLUSTRATED DEFINITIONInertia
The tendency of a moving mass to resist a change in motion. In electricity systems, energy in synchronously connected rotating machinery can initially oppose rapid frequency changes after a power imbalance.
ILLUSTRATED DEFINITIONWater pressure
The force exerted per unit area by water. In a distribution network, elevation, pumping and losses along the flow path help determine the pressure available at a particular location.
ILLUSTRATED DEFINITIONWater flow rate
The volume of water passing a point during a stated time interval. Comparing inflow and outflow reveals whether a store is filling, emptying or holding a constant volume.
ILLUSTRATED DEFINITIONStorage
A resource held for later use, such as water in a reservoir or energy in a battery. Usable inventory, delivery limits and replenishment determine what service that store can support.
ILLUSTRATED DEFINITIONResilience
The ability to prepare for disruption, withstand its effects, adapt and recover. It depends on equipment, people, arrangements and supporting services, and can include maintaining a reduced but useful service.
ILLUSTRATED DEFINITIONRedundancy
Additional equipment or paths able to support a function if another becomes unavailable. Their value depends on usable capacity, operating arrangements and whether the same event can disable the alternatives together.
ILLUSTRATED DEFINITIONDependency
A reliance on another resource, service or system to perform a function. The relationship can exist within one network or across sectors, and its effects depend on available alternatives and buffers.
ILLUSTRATED DEFINITIONBuffer
An available inventory or margin that absorbs a temporary mismatch. Water storage can bridge unequal inflow and outflow, while spare timetable time can absorb extra occupation before a constraint becomes limiting.
ILLUSTRATED DEFINITIONBottleneck
The constraint that limits the rate a connected process or service can sustain under the current conditions. Increasing capacity elsewhere may have little effect until that limiting constraint changes.
ILLUSTRATED DEFINITION