The universal symbols for on and off power are defined by the IEC 60417 standard: a solid vertical line (|) for 'On' (5007), an empty circle (O) for 'Off' (5008), and a circle broken by a vertical line (⏻) for 'Standby/Soft Off' (5009). If you are designing an enclosure, wiring a chassis, or troubleshooting a faded control panel, knowing the exact difference between a hard mains disconnect and a logic-level standby switch is the difference between a safe repair and a lethal shock.
The Complete IEC 60417 Power Symbol Reference Table
Before wiring or designing, verify your switch type against this table. These glyphs are standardized globally for user interfaces, but their electrical implications vary drastically.
| Symbol (Unicode) | IEC 60417 Ref | Meaning in Practice | Electrical Action | Typical Application |
|---|---|---|---|---|
| | (Line) | 5007 | Power On (Hard) | Closes main power circuit; full voltage applied. | Mains rockers, industrial contactors. |
| O (Circle) | 5008 | Power Off (Hard) | Physically breaks the circuit; 0V on load side. | Appliance mains disconnects, PSU inputs. |
| ⏻ (Broken Circle) | 5009 | Standby / Soft Off | Switches logic signal or secondary side; primary mains remains LIVE. | TVs, PC front panels, smart home devices. |
| ⏽ (Line in Circle) | 5010 | On/Off Toggle (Push) | Momentary push-button that toggles state via latch or microcontroller. | Computer power buttons, modern appliance touch panels. |
Regional and Standard Variants (IEC vs. IEEE vs. NEMA)
While IEC 60417 governs the physical UI glyphs printed on consumer and commercial equipment, engineering schematics and industrial panels often rely on different standards. Do not confuse a UI legend with a schematic symbol.
- IEC 60417 / ISO 7000 (Global UI): The |, O, and ⏻ symbols you see molded into plastic rockers. Governed by the International Electrotechnical Commission. Mandatory for CE-marked consumer goods sold in the EU and widely adopted globally.
- IEEE 315 / ANSI Y32.2 (US Schematics): In US electrical schematics, you will rarely see the | or O glyphs. Instead, power switching is denoted by standard SPST (Single Pole Single Throw) or DPST switch symbols with explicit line breaks indicating the physical air gap. See the All About Circuits switch reference for exact schematic drafting.
- NEMA / IEC 60947 (Industrial Control): On industrial 480V motor control panels, UI symbols are often abandoned in favor of strict color-coding (Red for Off/Stop, Green for On/Start) accompanied by literal text ('START' / 'STOP') to eliminate cross-lingual ambiguity in high-hazard environments.
The 'Rows People Get Wrong' Notes
When reading the reference table above, two specific rows cause dangerous misinterpretations on the bench and in the field.
The broken circle symbol does not mean the device is safe to service. In 95% of modern switch-mode power supplies (SMPS), the ⏻ button only switches the secondary DC side or sends a logic-low signal to a microcontroller. The primary side (120V/240V AC mains) remains connected to the bridge rectifier and bulk capacitors. If you open a chassis with the switch in the ⏻ position, you can still be killed by charged primary capacitors. Always unplug the device or use a hard-disconnect (O) switch before probing.
The Toggle Confusion (IEC 60417-5010 ⏽): Makers often assume the line-inside-circle symbol indicates a maintained physical switch. It almost always denotes a momentary action. Pressing it sends a brief pulse to a flip-flop circuit or MCU GPIO pin. If you are replacing a broken ⏽ switch on a PCB, do not wire in a standard maintained toggle switch; you will create a dead short or fry the logic latch. Use a momentary tactile or pushbutton switch.
Safe Interpretation When Markings Are Faded or Missing
On legacy equipment (e.g., 1990s audio amplifiers, old industrial relays), the silk-screen or molded plastic legends wear off. Never guess the switch state based on physical position alone. Follow this verification protocol:
- De-energize and Isolate: Unplug the device. If it has internal batteries, disconnect them.
- Continuity Test (Unpowered): Set your multimeter to continuity/ohms. Probe the switch terminals. Toggle the actuator. The position that reads <1.0 Ω is 'On' (|). The position that reads 'OL' (Open Loop) is 'Off' (O).
- Phantom Load Test (Powered): If the switch has 3+ terminals, it may be a standby logic switch. Power the device through a Watts Up meter or a smart plug with energy monitoring. If the 'Off' position still draws >0.5W, it is a standby (⏻) switch, meaning internal mains circuits are still live.
PCB and Product Design Decision Path
If you are designing a new product or replacing a chassis switch, use this decision tree to select the correct symbol and physical component. This path assumes a standard 120V/240V AC mains input environment.
| Design Requirement | Required Symbol | Switch Topology | Concrete Component Pick |
|---|---|---|---|
| Must physically isolate AC mains from the device for user safety (UL/CE requirement). | | / O (5007/5008) | DPST or SPST maintained rocker, rated for mains voltage and inrush current. | Carling V-Series V1D1 (20A 125VAC, I/O legend, snap-in). |
| Device needs to enter low-power sleep mode but wake via IR/Network; mains stays live. | ⏻ (5009) | SPST momentary tactile switch wired to MCU GPIO with internal pull-up. | C&K KSA Series (Sealed tactile, 12VDC logic level). |
| Space-constrained panel where a single button must toggle hard power via a latching relay. | ⏽ (5010) | Momentary pushbutton driving a bistable latching relay circuit. | TE Connectivity AVL Series (Illuminated momentary pushbutton). |
Default Recommendation: If you are building a custom enclosure for a DIY bench power supply or a high-wattage maker project and are unsure which to use, always default to the hard | / O disconnect (Carling V-Series). It provides a visible, physical air gap that guarantees safety during troubleshooting, eliminating the phantom-load hazards inherent to soft-switching standby circuits. For authoritative symbol vector files and compliance data, always refer to the ISO Online Browsing Platform (OBP) graphical symbols database before sending your enclosure design to manufacturing.
