> If you go for magnetic holding you could perhaps use very strong
> magnets to hold it in during use and get over the excessive removal
> force problem by having an eject button that fires up an electromagnet
> that briefly overwhelms the holding magnets to spit the connector out.
> There might be some interesting back EMF problems from the ejection
> coil as the power gets abruptly cut off though... and you don't want to
> go permanently  demagnetising your holding magnets either ... might
> work though :)


The is a fully mechanical version of that - http://www.tengtools.com.au/ima=
ges/D/119081008.jpg.  The knob rotates or moves the magnet so it loses it's=
 holding power, not exactly zero-force though.

No-volt safety switches work like you describe, although they are really a =
variation on a relay.

You can sell your electromagnet version as a safety feature, when the mains=
 power goes off the cord pops out, thus the tool won't start up when the po=
wer comes back.  I'm not sure I'd trust it over a no-volt switch box, but a=
nyway.

The problem with magnets in the context of the OP's question (power tools) =
is metal grit getting into everything.  With the indicator holder linked it=
's not much of a problem as the grit can be brushed off, or at least moved =
around to the side when it won't get in the way.

There is a bit of grumbling with this happening with Apple's MagSafe connec=
tor, but not many people tend to use their Macbooks next to a chopsaw, so i=
t's rare.

Tony


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