Card payment terminals use the network for card authorization, but depending on the merchant agreement with its card processor, authorization (at least back in my day) was typically only needed for charges above say $50. Otherwise the bank would pay up and eat the loss if something went wrong. If you’re old enough to remember cards with raised numbers on them, those existed so the merchant could make an imprint of the card number on carbonless paper using a hand operated gizmo with rollers and carbonless forms. That used no electricity at all. You’d sign the piece of paper and the merchant would turn it in to the bank. That was simply how credit cards worked for quite a long time. Electronic terminals, and especially portable electronic terminals came along later.