1)What would you do with a "Killswitch"? And where would you find it? and 2)It has a less scarey title in the Book what is it?

A kill switch, or emergency stop, or "e-stop," is found on many devices to shut them off in emergencies / life threatening situations.

Having worked in a few factories, I can definitely say that Fuse is right. All sorts of machinery in factories, large and small, have kill switches. There are also kill switches in radio station studios. (MrsS may have better information on radio stations; she was a DJ for a while.)

As you have spotted the othe applications I'll tell you the Other answer to my question
Is is Fitted to 99% of large Motorcycles and is often Labelled RUN-STOP Hence the tag Run/stop switch
Further info.. Many sports bikes have a socket fitted with the end attached to the rider so if they take a tumble the engine cuts out and reduces the rider(or bystander) being hit by a spinning wheel
Always puzzles me why they are not fitted to high performance road bikes too Only a cheap thing to make up

PS I vaguely remember reading that this method was called a "Kill wire"!

Having worked in factories as a student during the summer bedstor, while I was at university, I will add that I was thinking of the emergency switch in factories too.

There were at least a couple of occasions when, while working a double shift, and being overly tired, so not paying attention, I was glad that switch was there.