On Tue, 25 Jul 2017 02:40:30 -0700 (PDT), JohnW
wrote:

Mine has a safety feature in that if you touch the fan cage the motor stops but continues to hum.

Ooerr. Hmm, often when I've been testing it it's just been resting on
the sofa (on it's cage).

This feature broke once and the fan just hummed when I switched it on.

Ok.

There was a connection to the frame that had gone open circuit. I cant remember the details of how it worked but there was a single connection to the frame and some sort of proximity detector.

Whilst it would be good to think this one had such a feature, I've had
it all apart and didn't see anything that looked like it would do that
('electronics' etc). ;-(

Cheers, T i m