rotate bytes in array

[Demon]

Yes, the device is also a car alarm that is triggered by internal lights that come on when the vehicle door is opened.
...

Just a technicality; I'd feed directly from the door switch, not the lamp itself. You could have forgotten the interior lamp switch in the OFF position, the lamp could be burnt, or the robbers might know this trigger; they could just break the window, turn off the lamps and open the door.

I know it's highly unlikely, but it would make your device even better.

Robert

[Art]

It does get it's input from the door switch
It's live until any door is opened, then it is earthed.
That is why I might get a false trigger as the batteries die.