(FORTUNE Magazine) – July was a hectic month for Lexicon, a small manufacturer of electronic terminals and modems that link computers over phone lines. In less than two weeks the Fort Lauderdale, Florida, company was selected by both MasterCard International and American Express to develop cheaper but smarter versions of the terminals retailers use to validate credit cards automatically. A retailer punches the amount of a sale into the device and passes the customer's card through it. The terminal, which will cost less than $100, is connected by phone with the card issuer's computer. Industry analysts say the contracts could yield $60 million in sales over three years. Lexicon is expected to earn $800,000 on sales of $8 million in the fiscal year August 31. Its stock was recently selling for $3.25 a share, down from a high of $5.188 in 1983.