>Also, what happens when the button wears out or malfunctions? You have multiple buttons, and have marginally longer lines until someone can come to fix it. Or

>Also, what happens when the button wears out or malfunctions? You have multiple buttons, and have marginally longer lines until someone can come to fix it. Or if that would cost you too much in sales, you have a regular maintenance schedule that reduces the chance of failure to acceptable levels. (And still involves far less labour than paying for a cashier all day.)