According to https://en.wikipedia.org/wiki/Power_symbol#Standards, "one inside a circle", IEC 60417-5010, is a fully-on/fully-off toggle. The "one breaking a circle" symbol, IEC 60417-5009, is a fully-on/standby toggle.
“Standby symbol ambiguity
Because the exact meaning of the standby symbol on a given device may be unclear until the control is tried, it has been proposed that a separate sleep symbol, a crescent moon, instead be used to indicate a low power state. Proponents include the California Energy Commission and the Institute of Electrical and Electronics Engineers. Under this proposal, the older standby symbol would be redefined as a generic "power" indication, in cases where the difference between it and the other power symbols would not present a safety concern. This alternative symbolism was published as IEEE standard 1621 on December 8, 2004.”
Edit: formatting, verbosity.
This may have been avoided owing to strong potential of religious misinterpretation.