Computers do not read and the reason this works is that the line you sign on has to have a signature. Years ago in warranty repair work if nobody was there we signed the ticket with "door open" and it always worked. In many cases today the amount of money involved determines if a person has to sign or not. In my current job I have to have a signature when I deliver the parts. Some who have credit cards on file with us have protested this signing to the main boss and he says it is OK to simply leave the parts and ticket with them. They are "on file" and choose NOT to sign all the time.