Power Symbol Discussed at #UTC138

Our proposal to include the IEC Power Symbols of ⏻ ⏼ ⏽ ⭘ ⏾ in to Unicode was formally discussed today at Unicode Technical Committee 138.

So, how did it go?

The good news is that the moderator thought the proposal was well formed and that there was no objection to including POWER and POWER ON-OFF .

There was some discussion as to whether the existing Unicode Moon character – ☾ – would suffice for the SLEEP symbol . We think that the semantic meaning is sufficiently different to warrant inclusion – not to mention that crescent and quarter are very different phases of the moon.

Of more concern was the proposal that our ⏽ & ⭘ characters be “unified”. That means they can adequately be represented by other code-points within the Unicode specification. Obvious candidates would be the pipe symbol | and the capital letter O.

We think that unification could be a problem. ISO defined all these symbols to be distinctive and also to be visually cohesive. Recycling characters makes their use more complicated. Searching through a document for the specific character will be a lot easier than wading through all the “O” characters.

We are now awaiting the committee’s ad hoc group to report back to us.

For a more complete picture of what went on, here are Joe’s minutes:


Conference call opened at approximately 1110 AM PST; Joe Loughry, Bruce Nordman, and Terence Eden were all present on the call.

The moderator said the proposal was well formed.

Discussion of unification: several members thought the POWER ON symbol could be unified with ASCII vertical bar, and POWER OFF could be unified with any of several existing circles. There was not uniform agreement, however; at least one member thought that unification would be a bad idea; not just unnecessary, but undesirable because of the potential for confusion.

Discussion of moon phases: the committee members seemed to appreciate that the phase of the moon (last crescent) is significant, and there is no other waning crescent moon symbol to unify it with. Bruce Nordman noted that the moon phase was deliberately chosen by IEEE 1621 to be distinctive.

Discussion of circles and vertical lines: there is no objection to the POWER or POWER ON-OFF symbols, but the vertical line and circle symbols are candidates for unification. There was some discussion of the way the symbols all go together visually, and it would be desirable not to unify the circle and vertical line for that reason alone. Joe Loughry spoke up to argue in favour of not unifying any of the symbols, as it would make them not as easily searchable in technical documentation, particularly as the POWER symbol and ASCII vertical bar would very likely both appear in technical documents, and could be confused.

Discussion of names: SLEEP might better be called SLEEP POWER MODE.

There was a question about whether the moon symbol should be mirrored for right-to-left scripts; Bruce Nordman noted that the symbol is mostly used on equipment, which is used worldwide, and it would not be mirrored on that equipment. The moderator then agreed that the symbol should not be mirrored.

Bruce mentioned that the IEC has a standard template for drawing symbols. This is included in the “precise drawing” of the sleep symbol that can be found at http://energy.lbl.gov/controls/publications/pubsindex.html

The specifics of this are included in another document on that page on “Designing the new Moon Symbol“.

Discussion of shapes: objection that there are no attestations showing distinctive shapes of POWER OFF and POWER ON; writers before now have used any old vertical bar and circle they could find in their fonts to represent them.

Joe noted that the symbols need not be contiguous in the Basic Multilingual Plane (BMP) as they do not specify an implied order.

Overall, there was agreement that POWER and POWER ON-OFF are uncontroversial and should be adopted; SLEEP probably ought to be adopted; and POWER ON and POWER OFF might be unified with existing vertical bar and open circle symbols, although there are good reasons, related to confusion, not to unify them.

The committee asked for a counter-proposal regarding unification; an ad hoc group will meet today at lunchtime about it. They will contact us.

The moderator reiterated that the proposal was well prepared and well thought out.

Call ended 1130 AM PST.


Well, there you have it! I’ll update this blog when we know more.

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