Further to the interpretation of the "O" and 
"|" symbols:

    http://ask.metafilter.com/28272/the-circle-line

Be sure to explore the links in the page.

Note that most people have no idea what the 
"O" and "|" symbols mean or even that the 
symbols are from standards.  

Other related articles:

    http://www.eepn.com/Locator/Products/Index.cfm?Ad=1&ArticleID=31710
    http://www.energy.ca.gov/reports/2003-10-31_500-03-012F_APP.PDF

In this last reference, IEC symbols are given,
but the applications (uses) are not those given
by the IEC.  Such published divergences create 
confusion as to the use and intent of the symbols
as demonstrated in the first URL.

Standards committees spend hours debating symbols
and fine-tuning their definitions.  Then, 
designers use their own interpretations.  Users
have difficulty interpreting the symbols, but 
quickly learn through use of the equipment.

Consider these power state modes:

    On
    Off
    Standby
    Hibernate
    Sleep

"On" and "off" are reasonably clear.  How are the
other modes differentiated?  Who (user) cares?  
Why do we need any differentiation (from a 
functional point of view)?  


Enjoy!
Rich

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