How did they know back when the credit card machines were manual that the card was still good?

Question

I know that for really big amounts they called the credit card company. But did they also do it for small amounts of $10-$20? And if so how did it work in a Taxi when there were no mobile phones?

In: 1

Answer 1

Back in 1971 I worked in a department store…they had a newspaper type booklet with published bad card numbers and you had to look it up. If the number was in the booklet, it was not usable. Fine print and the size of a small paperback