Electrical symbols: US and IEC side by side

Limits current and drops voltage in proportion to the current through it (Ohm’s law). The most common part on any schematic.

The zigzag is the US form; IEC 60617 draws a plain rectangle. IEEE 315 also allows the rectangle, so US schematics drawn in modern CAD tools sometimes use it too. Either way the value goes beside the symbol, often in RKM code: 4k7 means 4.7 kΩ.

Also called: fixed resistor, resistance, zigzag, rectangle resistor

A two-terminal resistor whose value can be changed, used to set a current or trim a circuit.

An arrow drawn through any symbol means “adjustable” in both standards; only the resistor body changes. A preset trimmer is often drawn with a short bar (a T) instead of an arrowhead.

Also called: rheostat, adjustable resistor, trimmer

A resistor with a third, sliding terminal (the wiper), drawn as an arrow pointing at the body. Volume controls, setpoint knobs and sensor trims.

Same arrow-to-body convention in both standards. With the wiper tied to one end, a potentiometer becomes a rheostat.

Also called: pot, trimpot, wiper, voltage divider

A resistor whose value changes strongly with temperature. NTC types fall as they warm (temperature sensing, inrush limiting); PTC types rise (resettable fuses, motor winding protection).

Both standards add a slanted line with a short foot, meaning the value varies non-linearly with a physical quantity. IEEE 315 marks it t°; IEC uses θ (or t°), with −θ for NTC and +θ for PTC.

Also called: NTC, PTC, temperature sensor, thermal resistor, inrush limiter

A resistor whose resistance drops in light. Dusk-to-dawn photocontrols on outdoor lighting and simple light sensors.

Arrows pointing in mean “responds to light” in both standards; arrows pointing out mean “emits light”, as on an LED.

Also called: LDR, light-dependent resistor, photocell, CdS cell, photoconductive cell

Two plates separated by an insulator: stores charge, blocks DC and passes AC. Decoupling, filtering, timing, motor starting and power-factor correction.

Two equal straight plates in both standards. IEEE 315 also has a style with one curved plate, still common on older US drawings, where the curve marks the outer foil or the negative side.

Also called: cap, condenser, non-polarized capacitor, ceramic capacitor, film capacitor

A capacitor that must be connected the right way round, such as aluminium electrolytic and tantalum parts. Power-supply smoothing and bulk energy storage.

The + mark is what matters. US schematics usually draw the negative plate curved; IEC uses two straight plates with a + beside the positive one. Old German drawings showed the plates as an open and a filled rectangle.

Also called: electrolytic capacitor, e-cap, tantalum capacitor, polarised capacitor, bulk capacitor

A capacitor whose value is set by turning a shaft or trimmer screw, for tuning radio circuits and trimming oscillators.

Same in both: the adjustable arrow through the plates. A varicap (varactor) is a different part: a diode used as a voltage-controlled capacitor.

Also called: tuning capacitor, trimmer capacitor, air-variable capacitor

A coil of wire that stores energy in its magnetic field and opposes changes in current. Filters, chokes and switching converters.

Both standards draw a row of half-circles; four is usual, and the count means nothing. Hand-drawn US schematics often use looped curls instead.

Also called: coil, choke, winding, reactor

An inductor wound on a magnetic core for far more inductance per turn: line reactors, ballasts and mains chokes.

A straight line beside the winding means a magnetic core. US drawings often use two lines; IEC uses one. Many US drawings use dashed lines for a ferrite or powdered-iron core.

Also called: choke, reactor, line reactor, ferrite-core inductor, magnetic-core inductor

Two or more windings coupled by a shared magnetic field: steps AC voltage up or down and isolates circuits. Control transformers, power supplies and utility services.

US schematics draw two facing windings. IEC drawings, especially single-line diagrams, draw two overlapping circles, one per winding; IEC also has a winding form for detailed diagrams.

Also called: XFMR, xformer, TX, trafo, isolation transformer

The everyday power transformer: windings on a laminated steel core. Control-circuit transformers (480 V to 120 V), doorbell and HVAC transformers, wall adapters.

The core is drawn between the windings: two lines on most US drawings, one line in the IEC winding form. IEC single-line diagrams usually use the two-circle form and leave the core out.

Also called: power transformer, control transformer, mains transformer, laminated-core transformer

A slice of quartz between two electrodes that resonates at a precise frequency: the clock source for microcontrollers, radios and real-time clocks.

Same in both standards. Ceramic resonators use a similar symbol, often with a third (ground) terminal.

Also called: XTAL, quartz crystal, crystal oscillator, resonator, piezoelectric crystal

A conductor designed to melt and open the circuit on overcurrent. Branch-circuit, equipment and control-circuit protection.

The S-curve is the traditional US symbol. IEC draws a rectangle with the conductor running straight through it, which keeps it distinct from a resistor; IEEE 315 accepts that form too.

Also called: cartridge fuse, fusible link, fuse link, blade fuse

A resistor whose resistance collapses above a threshold voltage, clamping surges. Inside surge protective devices and across relay coils, contactors and power inputs.

Both standards use the resistor with the non-linear line, marked with the quantity it responds to: V on US drawings, U (the IEC letter for voltage) on IEC drawings.

Also called: MOV, metal-oxide varistor, VDR, voltage-dependent resistor, surge suppressor

Lets current flow one way only, from anode (triangle) to cathode (bar). Rectifiers, reverse-polarity protection, flyback diodes across relay coils.

Same in both standards. The triangle may be filled or open; the bar matches the band printed on the part. The triangle points the way conventional current flows.

Also called: rectifier diode, rectifier, PN junction, signal diode

A diode that emits light when forward-biased; the arrows point away to show light leaving. Indicators, lighting and optocouplers.

Same in both standards. An LED needs a series resistor or a constant-current driver to set its current.

Also called: light-emitting diode, indicator, diode light

A diode that passes current in proportion to the light falling on it; the arrows point in. Light meters, optical receivers and smoke detectors.

Same in both. Do not confuse it with an LED: the arrow direction is the only difference.

Also called: light sensor, photo sensor, PIN photodiode

A diode built to conduct in reverse at a set breakdown voltage: a simple voltage reference, clamp or regulator.

US drawings usually bend both ends of the bar into a Z (IEEE 315 also allows a single bent end); IEC uses one short stroke at one end. Write the voltage beside it, such as 5V1 for 5.1 V.

Also called: Zener, breakdown diode, voltage reference diode, avalanche diode

A fast diode with a low forward voltage (roughly 0.2 to 0.5 V). Switching power supplies, solar bypass diodes and battery OR-ing.

Same in both: the bar ends in small S-shaped hooks.

Also called: Schottky barrier diode, hot-carrier diode, SBD

A diode built to absorb fast voltage spikes; the bidirectional type clamps both polarities. Protects data lines, DC inputs and control wiring.

Same in both: two breakdown diodes back to back sharing a Z-shaped bar. A unidirectional TVS uses the Zener symbol.

Also called: transient voltage suppressor, ESD diode, surge diode, bidirectional breakdown diode

Four diodes arranged so that AC in gives DC out on both half-cycles. Power supplies, battery chargers and DC coil supplies.

Same in both. Block diagrams often shrink it to a square split by a diagonal, with ~ on the input side and = on the output side.

Also called: diode bridge, full-wave bridge, rectifier bridge, Graetz bridge

A bipolar transistor switched on by current into the base; the emitter arrow points out. Small-signal amplifiers, relay and LED drivers.

Same in both standards; the circle (envelope) is optional in both. Memory aid: NPN, “not pointing in”.

Also called: BJT, bipolar junction transistor, NPN

The complementary bipolar transistor: the emitter arrow points in, and it turns on when the base is pulled below the emitter. High-side switches and push-pull stages.

Same in both. In real circuits a PNP is usually drawn with the emitter at the top, toward the positive rail.

Also called: BJT, bipolar junction transistor, PNP

A voltage-controlled switch: a positive gate-to-source voltage turns it on. The broken channel line means enhancement mode, off at zero gate voltage.

Same in both. The arrow on the body connection points in for N-channel. Datasheets usually add the built-in body diode between drain and source.

Also called: NMOS, power MOSFET, logic-level MOSFET, N-MOSFET, IGFET

Turns on when the gate is pulled below the source. Common as a high-side switch and for reverse-polarity protection.

Same in both. The body arrow points out for P-channel.

Also called: PMOS, P-MOSFET, IGFET

A junction FET that conducts with zero gate voltage and is pinched off by a negative gate. Low-noise amplifiers and analog switches.

Same in both. The solid channel line marks a depletion device; the gate arrow points in for N-channel and out for P-channel.

Also called: junction FET, N-JFET, depletion-mode FET

An insulated-gate bipolar transistor: a MOSFET-style gate driving a bipolar output. The main switch in VFDs, inverters, welders, induction heaters and EV drives.

Same in both: an insulated gate like a MOSFET, with a collector and an arrowed emitter like a BJT.

Also called: insulated-gate bipolar transistor, power switch

A diode that stays off until a gate pulse turns it on, then latches until the current falls to zero. Controlled rectifiers, soft starters and crowbar circuits.

Same in both; the gate lead leaves from the cathode side.

Also called: thyristor, silicon-controlled rectifier

An AC switch: two thyristors in inverse parallel sharing one gate. Light dimmers, fan speed controls and solid-state relays.

Same in both. The terminals are MT1, MT2 and the gate; the gate is referenced to MT1.

Also called: bidirectional thyristor, TRIAC, AC switch

A two-terminal trigger device that conducts in either direction once the voltage passes its breakover point (around 30 V). It fires the triac in a dimmer.

Same in both: a triac with no gate.

Also called: DIAC, trigger diode, bidirectional trigger diode

An LED and a phototransistor in one package: it passes a signal by light while keeping the two sides electrically isolated. Power-supply feedback, PLC inputs, isolated interfaces.

Same in both; the box marks a single package. The output side varies: phototransistor, photo-triac or logic gate.

Also called: opto-isolator, photocoupler, optoisolator, opto

A high-gain differential amplifier with inverting (−) and non-inverting (+) inputs. With feedback it amplifies, filters, buffers, sums and integrates.

US practice is the triangle. IEC 60617 draws a rectangle with a small triangle and ∞ (very high gain) inside, though many European schematics also use the triangle.

Also called: op amp, opamp, operational amplifier, amplifier

Compares two voltages and drives its output high or low depending on which is larger. Battery monitors, thermostats, zero-cross detectors and window comparators.

Drawn as an amplifier triangle, exactly like an op-amp; the part number, a COMP label or a small step mark inside (as here) tells them apart. Many comparators have an open-collector output that needs a pull-up resistor.

Also called: voltage comparator, comparator IC, LM393

Output is 1 only when every input is 1. Interlocks: run only if the guard is closed and the start is pressed.

IEC 60617-12 uses a rectangle marked & (“and”). IEEE 91 brought the IEC rectangular forms into the US standard, but the older curved shapes still dominate US textbooks, schematics and datasheet diagrams.

Also called: AND, logical AND, conjunction

Output is 1 when at least one input is 1. Any of several stop or alarm conditions.

IEC writes ≥1: the output is true when one or more inputs are true.

Also called: OR, logical OR, disjunction

Output is the opposite of the input. Turns active-low signals into active-high ones.

The small circle means inversion in both styles. IEC marks the box 1 (a buffer) and puts the circle on the output.

Also called: inverter, NOT, negation

An AND gate with an inverted output: 0 only when every input is 1. Any logic function can be built from NAND gates alone.

Both styles add the inversion circle to the AND symbol.

Also called: NAND, not-AND, universal gate

An OR gate with an inverted output: 1 only when every input is 0. Also a universal gate.

Both styles add the inversion circle to the OR symbol.

Also called: NOR, not-OR

Output is 1 when the inputs differ. Parity checks, adders and two-way (three-way US) switching logic.

US adds a second curved line at the inputs. IEC writes =1: exactly one input must be true.

Also called: exclusive OR, EOR, EXOR

Output is 1 when the inputs are equal. Equality comparators.

An XOR with an inverted output. For two inputs some IEC drawings mark the box = (logic identity) instead.

Also called: exclusive NOR, equivalence gate, ENOR, EXNOR

An ideal source that holds a fixed voltage whatever current is drawn. Circuit-analysis and simulation diagrams use it for supplies.

US textbooks mark + and − inside the circle. IEC 60617 draws the conductor straight through the circle (an ideal source has zero internal resistance) and marks polarity outside. Real supplies are often drawn as a battery.

Also called: ideal voltage source, DC supply, independent voltage source, VDC

A sinusoidal voltage source: the mains supply, a utility feed or a signal generator in a schematic.

Same in both; IEC may write the AC sign ~ inside the circle. Write the voltage and frequency beside it (120 V 60 Hz, 230 V 50 Hz).

Also called: AC source, sine source, AC supply, signal generator, VAC

An ideal source that forces a fixed current whatever the voltage. Models transistor outputs, LED drivers and 4–20 mA sensor loops.

US: a circle with an arrow inside showing the current direction. IEC 60617: a circle crossed by a line at right angles to the conductor (infinite internal resistance), with the direction marked outside.

Also called: ideal current source, constant-current source, independent current source

Two or more cells in series. The long thin plate is positive and the short thick plate negative.

Same in both. The drawing need not show the real number of cells: write the voltage beside it (12 V). A dashed line between two cells also means “more cells here”.

Also called: battery pack, cells, accumulator, DC source

A single electrochemical cell, such as a 1.5 V alkaline, a 3 V lithium coin cell or a 3.6 V lithium-ion cell.

Same in both: long line positive, short line negative.

Also called: single cell, coin cell, button cell, primary cell

A cell that produces current from light. PV modules are many cells in series; PV system drawings usually show a module or array as a box with the cell symbol.

Same in both: a cell with incoming light arrows.

Also called: photovoltaic cell, PV cell, solar panel, PV module

A connection to the earth itself, through a ground rod or the grounding electrode system. On power drawings it marks the grounding electrode connection.

Same in both (IEC: earth, general symbol). Electronics schematics often use it loosely for circuit common; save it for real earth connections.

Also called: ground, earth, grounding electrode, GND

A connection to the metal frame or enclosure of the equipment, which may or may not be connected to earth.

Same in both (IEC: frame or chassis).

Also called: frame ground, chassis, frame, case ground

The reference point for signal voltages in electronics, often kept separate from noisy power returns and the safety ground until a single point.

The hollow triangle is IEEE 315’s signal (low-noise) ground. IEC has no triangle; its nearest symbol is functional (noiseless) earth, the earth sign under an arc, and many IEC schematics just label the net 0 V.

Also called: signal common, analog ground, AGND, 0 V, reference ground, common

The safety earth connection that carries fault current and keeps exposed metal at earth potential. Marks the PE terminal on equipment and in panels.

Same in both: the earth sign in a circle (IEC 60417-5019), also used on US equipment. In US wiring terms this is the equipment grounding conductor.

Also called: PE, protective ground, safety ground, equipment grounding conductor, EGC, earth terminal

Opens or closes one circuit: single pole, single throw. Light switches, power switches.

US drawings put small open circles at the terminals. IEC draws the moving contact as a slanted line from the conductor, with no circles.

Also called: on-off switch, single-pole single-throw, toggle switch, make contact, single-pole switch

One common terminal connects to either of two others. Selector switches; in house wiring, the US three-way switch is an SPDT.

IEC draws the normally closed side as a hooked contact that the blade rests on. Watch the naming trap: a US “three-way” switch is a UK “two-way” switch.

Also called: changeover switch, single-pole double-throw, two-way switch, three-way switch, transfer contact, form C

Two SPDT switches operated together. Motor reversing, polarity swapping and switching two lines at once.

The dashed line means “operated together” in both standards.

Also called: double-pole double-throw, reversing switch, two-pole changeover

Closes only while pressed. The start button in a motor control circuit, a doorbell push.

US: a bridging bar above two terminals, with a stem to push it down. IEC: a make contact with a dashed link to the push actuator.

Also called: push-to-make, momentary switch, NO push button, start button, pushbutton

Opens only while pressed. The stop button in a three-wire motor control circuit, emergency stops (with a latching head).

US: the bar sits under the terminals, touching them. IEC: a break contact with the push actuator.

Also called: push-to-break, NC push button, stop button, momentary NC

A switch worked by machine motion, such as a door, cam or moving carriage, to confirm a position or stop travel.

Both mark the actuator with a small wedge on the moving contact: IEEE 315 hangs the open blade below the terminals with the wedge underneath; IEC draws a make contact with a small triangle touching the blade.

Also called: position switch, travel switch, LS, end switch, micro switch

The electromagnet that operates a relay’s or contactor’s contacts. Its label (CR1, K1, M) ties it to its contacts elsewhere on the drawing.

US ladder diagrams draw the coil as a circle with its tag inside. IEC uses a rectangle, and so does IEEE 315 itself; electronic schematics often draw a box or an inductor next to the contacts.

Also called: coil, operating coil, solenoid, control relay, CR, K

A relay contact that closes when its coil is energized. Contacts are always drawn in the de-energized (shelf) state.

US ladder: two parallel lines. IEC: the make contact, the same symbol as a switch.

Also called: NO contact, make contact, form A, normally open

A relay contact that opens when its coil is energized.

US ladder: the parallel lines with a diagonal slash. IEC: the break contact with its hooked fixed contact.

Also called: NC contact, break contact, form B, normally closed

A heavy-duty relay that switches motor and power circuits; its main contacts carry the load current and its coil sits in the control circuit.

US drawings use the same contact as a relay, tagged M for a motor starter. IEC adds a small half-circle to the fixed contact: the contactor function mark.

Also called: magnetic contactor, motor starter, main contact, power contact

An automatic switch that opens on overcurrent and can be reset. Panelboard breakers, MCBs, molded-case and power breakers.

US: an arc bridging two terminals (IEEE 315); US single-line diagrams also draw power breakers as a small square. IEC: a switch with a cross on the fixed contact.

Also called: breaker, CB, MCB, MCCB, molded-case circuit breaker

Senses motor current by heating and opens its control contact if the motor stays overloaded too long. Part of every motor starter.

IEEE 315 draws the thermal element as a stepped line in the conductor, and IEC puts the same step inside a rectangle. US motor-control drawings tag the heaters and their normally closed contact OL.

Also called: overload relay, OL, overload heater, bimetal overload, thermal relay

A manual switch that isolates equipment for maintenance. Unless it is rated for load break, open it only after the load is off.

US drawings use the knife-switch blade and label it. IEC adds a short bar across the fixed contact for a disconnector (isolator).

Also called: disconnect, isolator, isolating switch, safety switch, disconnector, switch-disconnector

Trips when the current going out on the line conductor does not all come back on the neutral, because some is leaking to earth, possibly through a person. Personnel protection trips at 4–6 mA (US Class A GFCI) or 30 mA (IEC RCD).

US drawings have no special GFCI symbol in everyday use: they label a breaker or receptacle GFCI (or GFI). IEC drawings show the contacts linked to a residual-current release marked IΔ, with both conductors passing through a sensing core.

Also called: GFCI, GFI, RCD, RCCB, RCBO, ground-fault circuit interrupter, residual current device, earth leakage breaker, ELCB

A circle with M. On power drawings it sits at the end of the branch circuit with its horsepower or kilowatts and full-load current beside it.

Same in both. IEC adds the supply: M 3~ for a three-phase motor; US drawings often write the horsepower inside or beside the circle instead.

Also called: electric motor, induction motor, MTR, M

Standby and prime-power generators on single-line diagrams, alternators on engines and turbines.

Same in both; G 3~ for a three-phase alternator.

Also called: GEN, alternator, genset, standby generator

A lamp or indicator light. On control panels a pilot light usually carries a colour letter (R red, G green, A amber).

This is the classic US/IEC difference: IEC (and UK and European practice) draws a circle with a cross; US drawings show a filament inside the circle, and US ladder diagrams draw pilot lights as a circle with short light rays.

Also called: light, bulb, pilot light, indicator lamp, signal lamp, light fixture

A resistive element built to make heat: baseboard heaters, water-heater elements, enclosure and anti-condensation heaters.

US drawings use a resistor tagged HTR. IEC 60617 has its own heating-element symbol: a rectangle divided into cells.

Also called: heating element, resistance heater, space heater, element, HTR

Makes a tone or buzz when energized: alarm panels, appliance beepers, warning sounders.

The leads go into the curved side; on a bell they go into the flat side. Building plans and fire-alarm drawings use their own signalling symbols, so check the legend.

Also called: sounder, beeper, piezo buzzer, piezo sounder

An electromechanical bell: fire-alarm bells, doorbells, school and factory signals.

Same in both: a dome with the leads going into its flat side (a buzzer reverses it). A gong adds a line across the dome.

Also called: alarm bell, doorbell, chime, gong

Turns an electrical audio signal into sound: PA systems, voice evacuation, intercoms.

Same in both: a small rectangle (the magnet) with a flared cone.

Also called: speaker, loudspeaker, horn, PA speaker

Radiates or receives radio signals: Wi-Fi, cellular, GPS, two-way radio and broadcast reception.

Same in both. “Aerial” is the British word.

Also called: aerial, ANT, antenna

Measures voltage; connected in parallel, across the part being measured.

Same in both: a circle with the unit symbol. IEC uses a square for recording instruments and a rectangle for integrating meters such as kWh.

Also called: voltage meter, V

Measures current; connected in series, or through a current transformer on power circuits.

Same in both. Clamp meters measure current without breaking the circuit, but the diagram symbol is the same.

Also called: amp meter, ammeter, A

Measures real power. It has a current circuit in series and a voltage circuit in parallel.

Same in both. Detailed drawings show the current and voltage coils separately.

Also called: power meter, W

Measures resistance with its own internal source, so it is used only on de-energized circuits.

Same in both. An insulation-resistance tester (megger) is often marked MΩ.

Also called: resistance meter, megohmmeter, insulation tester, Ω

Displays voltage against time. Shown on test set-ups and lab diagrams.

Same in both: an instrument circle with a waveform inside.

Also called: scope, CRO, DSO

A standard two-outlet wall receptacle (NEMA 5-15R or 5-20R). Mounting height and circuit number are often written beside it.

One line through the circle is a single receptacle, three a triplex. IEC and UK plans draw a socket outlet as a half-circle instead.

Also called: duplex outlet, outlet, wall plug, convenience outlet, power point, socket outlet

A duplex receptacle with built-in ground-fault protection, required by NEC 210.8 in bathrooms, kitchens, garages, outdoors and the other locations it lists.

Usually the duplex symbol tagged GFCI or GFI; some offices fill the circle instead. WP is added for a weatherproof cover outdoors.

Also called: GFI outlet, GFCI outlet, ground-fault receptacle

A dedicated receptacle for a 240 V appliance: range, dryer, welder or EV charger.

Usually the special-purpose receptacle: a circle with a filled triangle. Practice varies (some offices use letters such as R for range or D for dryer), and good drawings write the NEMA configuration, such as 14-50R or 6-50R, beside it.

Also called: dryer outlet, range outlet, special-purpose receptacle, 240 volt outlet, 14-50R, 6-50R

A single-pole wall switch. A dashed arc on the plan links it to the lights it controls.

Subscripts tell the type: S3 three-way, S4 four-way, SD or SDM dimmer, SP switch with pilot light, SWP weatherproof, SK key-operated.

Also called: light switch, wall switch, S

One of a pair of switches that control the same lights from two places, such as the top and bottom of a stair.

Electrically it is an SPDT switch. In UK terms this is a two-way switch.

Also called: 3-way switch, S3, two-way switch (UK)

Goes between two three-way switches so the same lights can be controlled from three or more places.

Electrically it is a crossover (DPDT wired as a reverser). In UK terms this is an intermediate switch.

Also called: 4-way switch, S4, intermediate switch (UK)

A wall control that varies light output. Its type (incandescent, LED/CFL, 0–10 V) belongs in the fixture or device schedule.

Most legends write S with a D subscript; others use SDM or DIM. Check the legend, because on some older drawings the same letters meant a door switch.

Also called: dimmer, SD, SDM, DIM, S sub D

A surface-mounted ceiling lighting outlet or fixture. A letter inside or beside it keys it to the fixture schedule.

A plain circle is the traditional ceiling outlet; many offices add short rays or a letter. IEC and UK plans draw a light as a circle with a cross.

Also called: ceiling fixture, light outlet, ceiling outlet, luminaire

A wall-mounted lighting outlet or sconce, drawn with a short stem to the wall line.

The heavy line here stands for the wall. Exterior wall packs are tagged in the fixture schedule.

Also called: wall sconce, bracket light, wall fixture, wall outlet

A recessed downlight (can light) set into the ceiling. Fixture type and trim come from the fixture schedule.

Often drawn to scale: a small circle (or a circle in a square) for a downlight, a rectangle for a recessed troffer.

Also called: can light, downlight, pot light, recessed can, high hat

A ceiling fan or fan-light outlet. The box above it must be listed to support a fan, not just a light fixture.

Blades around a small circle; a fan with a light kit may combine this with the light symbol.

Also called: fan, paddle fan, ceiling fan outlet

A smoke alarm or detector. Dwelling alarms are interconnected so one sounding sets off all of them.

Fire-alarm drawings use their own legend (NFPA 170 symbols); residential plans usually just circle SD, with CO for carbon monoxide.

Also called: smoke alarm, SD, smoke detector, CO/smoke alarm

An outlet box used only for splices or a future connection, with a blank cover.

Drawn as J in a circle or in a small square. The NEC requires junction boxes to stay accessible, so one is never buried in a wall or ceiling.

Also called: J-box, junction box, splice box, pull box

A lighting or power panel; its tag (LP-1, PP-2, Panel A) matches the panel schedule.

Drawn as a long rectangle against the wall, partly or fully filled or hatched. What the fill means (flush or surface mounting, lighting or power panel) varies by office, so check the legend.

Also called: panel, electrical panel, breaker panel, load center, distribution board, consumer unit

The utility revenue meter (meter socket), usually on an exterior wall next to the service equipment.

Some offices use a circle with M, others a circle or rectangle with kWh. Tag it if there are several meters.

Also called: meter, meter base, meter socket, kWh meter, utility meter

The run from the last outlet back to the panel. The arrow points to the panel, and the tag names the panel and circuit (LP-1-3: panel LP-1, circuit 3).

Conventions vary by office: hash marks usually count the conductors (often only when there are more than two), some legends use one arrowhead per circuit, and marks for neutral and ground differ. Read the legend.

Also called: home run arrow, circuit to panel, HR