JohdotaAn indicator light shows the operator the state of the equipment, for example that a motor is running or that a protective device has tripped. Modern indicator lights are LEDs, and their voltage is chosen to match the control voltage.
Wiring
An indicator light has two terminals, X1 and X2. It is lit when the full control voltage is across it, that is, when one terminal is connected to line (L) and the other to neutral (N). The status is brought to the light through a contact, for example:
- a running light through an NO auxiliary contact of the contactor
- a fault light through the NO contact 97–98 of a thermal overload relay or the NC contact 21–22 of a motor protection circuit breaker.
Two indicator lights are not wired in series, because then neither of them gets the full voltage.
What the colours mean
- Red: emergency or dangerous condition.
- Yellow: abnormal condition that needs monitoring or action.
- Blue: the operator must take an action, for example a reset.
- Green: normal condition.
- White: any other condition, when none of the colours above fits.
In your region
Showing notes for
UK & Ireland
Machines in Great Britain are built to BS EN 60204-1, the European version of IEC 60204-1.
Source: UK government: designated standards for machinery (list v16, 2026)
Europe
Machines in Europe are built to EN 60204-1, the European version of IEC 60204-1. It is a harmonised standard under the Machinery Directive.
Source: European Commission: harmonised standards for machinery (summary list) · DIN Media: EN 60204-1:2018+A1:2025
Australia & New Zealand
Australia and New Zealand use AS/NZS 4024.1204, which is IEC 60204-1:2016 with national modifications.
Source: Standards Australia: AS/NZS 4024.1204:2019 (IEC 60204-1:2016 MOD)
Australia & New Zealand
The line conductor is called the active, so an indicator light is connected between active and neutral.
Source: Prysmian Australia: green/yellow is never an active or neutral (2016)
United States
Since the 2021 edition, NFPA 79 gives indicator lights the same meanings as IEC 60204-1: red emergency, yellow abnormal, blue mandatory action, green normal and white neutral.
On older panels a red light may mean that a motor is running, which is the opposite. Always check what the lights mean on each machine.
Source: NFPA 79 First Draft report, 2021 edition (Table 10.3.3, 9.1.1) · Siemens: Basics of Control Components, part 4 (STEP 2000 course)
United States, Canada
On ladder diagrams an indicator light is usually called a pilot light and marked LT. A letter inside the symbol can give the colour, such as R for red and G for green.
Source: Siemens: Basics of Control Components, part 1 (STEP 2000 course) · NFPA 79 First Draft report, 2024 edition (13.2.3, Annex E Table E.1 device designations) · Square D (Schneider Electric): Wiring Diagram Book 0140CT9201, symbols and examples
Canada
On older North American panels a red light may mean that a motor is running, which is the opposite of the IEC meaning. Always check what the lights mean on each machine.
Source: Siemens: Basics of Control Components, part 4 (STEP 2000 course)
Other IEC countries
No regional notes on this page yet. If something is different in your country, please send feedback.
Frequently asked questions
How do you wire an indicator light?
Connect X1 and X2 between line (L) and neutral (N) of the control voltage. The status comes through a contact, for example a running light through an NO auxiliary contact of the contactor.
What voltage indicator light should I use?
The same as the control voltage, for example 24 V or 230 V. The voltage is marked on the light or on its LED block.
What do indicator light colours mean?
Under IEC 60204-1, red means an emergency or dangerous condition, yellow abnormal, blue action required, green normal and white any other condition.
Can two indicator lights be wired in series?
Better not. In series, neither light gets the full control voltage. Wire indicator lights in parallel.
Sources
- Schneider Electric: push-button colours in IEC 60204-1 (2021)
- UK government: designated standards for machinery (list v16, 2026)
- European Commission: harmonised standards for machinery (summary list)
- DIN Media: EN 60204-1:2018+A1:2025
- Standards Australia: AS/NZS 4024.1204:2019 (IEC 60204-1:2016 MOD)
- Prysmian Australia: green/yellow is never an active or neutral (2016)
- NFPA 79 First Draft report, 2021 edition (Table 10.3.3, 9.1.1)
- Siemens: Basics of Control Components, part 4 (STEP 2000 course)
- Siemens: Basics of Control Components, part 1 (STEP 2000 course)
- NFPA 79 First Draft report, 2024 edition (13.2.3, Annex E Table E.1 device designations)
- Square D (Schneider Electric): Wiring Diagram Book 0140CT9201, symbols and examples