In message 
          Michael J. Mahon  wrote:

>Any ultrasonic receiver must be designed to reject typical interference to
>operate reliably. The transmitter technology (assuming mechanical
>generation of ultrasonic tones) is not a major factor, since both whistles
>and chimes both generate strong signals with good frequency stability.

Funny coincidence... I was vacuuming the gas fire yesterday, and it
suddenly turned on.

It has an ultrasonic remote control.

I assume that the loud noise of the air rushing into the cleaning
brush must have been such as to fool the receiver.

David

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