The US company Elcotel Inc. began testing a telephone system based on chip cards in 1995, but in reality a trial with inductive cards, of the type used in Brazil, was conducted the previous year. Two cards were used, 100 and 1000 units, both with the same design, which however have some interesting variations on the back.
The 100-unit card has a small square at the beginning of each sentence, while the 1000-unit card has a version with a dash, and one with a round dot, always before each sentence. It is therefore not excluded that the three variants exist for both values, which would lead to six different cards.
