SSO
Switched socket outlet
Plan mark for a socket outlet with its own integral switch that controls the supply to the plug.
IEC
IEC · SOI
Socket outlet with interlocked switch
Plan mark for an outlet whose switch is mechanically interlocked so a plug cannot be inserted or withdrawn while live.
In plain English
What does Socket outlet with interlocked switch mean?
Interlocked socket outlets are used for industrial plugs, welding outlets, portable plant supplies and higher-current three-phase outlets. The interlock forces the user to switch off before the plug can be removed or inserted, which prevents drawing an arc at the pins. The plan mark adds a switch stroke and a small interlock bar to the outlet form.
A simple example
On industrial layouts the symbol is often paired with a current rating and pole count written beside it, for example 32 A 5-pin. The estimator should expect a heavier enclosure, sometimes with an integral fuse or circuit breaker, and the installer should expect a surface-mounted accessory rather than a flush plate.
What the drawings help you do
The interlock mark does not confirm the presence of overcurrent or residual-current protection inside the unit. Check the schedule for combination units that include a breaker or RCD.
This particular reference
Plan mark for an outlet whose switch is mechanically interlocked so a plug cannot be inserted or withdrawn while live. A simple switched outlet allows the plug to be withdrawn while supplied with operating power; the interlocked form mechanically prevents it.
- Phase
- One of the related AC waveforms in a power system.
- Rating
- A value stating the conditions for which equipment is specified.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: IEC graphical symbols for diagrams · Elementary switching devices · Autodesk IEC-60617 preview: Single and duplex power-receptacle forms
IEC · Socket outlet with interlocked switch
IEC 60617 installation-plan style (architectural and topographical installation symbols); independently drawn, not certified IEC geometry or a database identifier.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
GA · SOI
What it represents
Interlocked socket outlets are used for industrial plugs, welding outlets, portable plant supplies and higher-current three-phase outlets. The interlock forces the user to switch off before the plug can be removed or inserted, which prevents drawing an arc at the pins. The plan mark adds a switch stroke and a small interlock bar to the outlet form.
On industrial layouts the symbol is often paired with a current rating and pole count written beside it, for example 32 A 5-pin. The estimator should expect a heavier enclosure, sometimes with an integral fuse or circuit breaker, and the installer should expect a surface-mounted accessory rather than a flush plate.
The interlock mark does not confirm the presence of overcurrent or residual-current protection inside the unit. Check the schedule for combination units that include a breaker or RCD.
How to read it
- Check the rating text: interlocked outlets are usually specified by current, poles and IP rating together.
- Do not confuse the interlock bar with the protective earth bar on a domestic outlet.
Information to show or reference
- State current rating, pole count and plug standard.
- State whether overcurrent or residual-current protection is integral.
- Note IP rating and mounting surface.
A distinction that matters
A simple switched outlet allows the plug to be withdrawn while energised; the interlocked form mechanically prevents it.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
IEC graphical symbols for diagrams
IEC committee context for graphical symbols used in diagrams and installation documents; not a source of reproduced artwork.
Elementary switching devices
Explains elementary switching functions such as isolation, control and functional switching.
Autodesk IEC-60617 preview: Single and duplex power-receptacle forms
Public receptacle family in an IEC-oriented CAD library, useful for comparing schematic receptacle forms with plan marks.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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