I forgot to mention in my last post a detail of the John Stalker advert for electric garage doors. Near the end he zaps the zapper to close it, but as it’s about three foot off the floor his dog comes bounding up.
Emergency! Fingernails to teeth — cute doggy is about to get sliced! Nope. Big selling-point is the infrared sensor that halts the door in its tracks allowing the dog to come tail-waggingly in to greet its master.
“Ha ha, you won’t do that again, will you?” says Stalker.
Of course it bloody will! Nothing happened, the door didn’t crush its spine, therefore nothing to fear. Even a bloody dog can work that one out.