muckles:
I’ve heard there were some that went to other work when you switched on the ignition, but I never driven a truck that did it.
I have no idea why a tacho should be set up this way, doesn’t seem a good reason for it.
On the contrary, sounds like a very stupid way to set it up, as it means that a driver that starts the truck to keep the battery charged (e.g. when boiling a kettle), or just turns on the ignition to enable an accessory (e.g. turn on the radio) would end up recording an interrupted rest and therefore be committing an infringement.