Do they record internally? Simple answer, no.
Punchy Dan:
F-reds:
Dan at no point did I say that they know if a chart is in for movement.But they can tell if the truck has been moved if the distance trace needle doesn’t match up on the charts before and after the movement, and if the peaks and troughs don’t match the stated mileage on the charts.
Ok ,it just reads that way ,
Doesn’t surprise me. I was, erm, full of seasonal cheer yesterday…
sort that out !
Thanks for the confirmation, although never realised there was a needle that didn’t just reset back to start everytime the engine was turned off or disk removed. Really got to study the disks a bit more as to be honest, I haven’t a clue what all those little squiggles actually mean. So much prefer the digi ones.
Mind you, the first time I used one many months ago, I managed to keep it squiggle free as forgot to put it under the plastic tab thingy - did wonder afterwards if it wrote in invisible ink. 
As for the tang disk - only thing I can see that’s an infringement is they’ve not filled in their name! 