Dial 'M' for money: Global Telecommunications pioneers plastic billboards. (prepaid phone cards; Global Telecommunications Solutions Inc.)(Telecommunications & Computers)

Prepaid phone cards, which have been wildly popular overseas since the '80s, were barely a novelty item in the United States in 1994.

How times have changed.

Now more than 500 companies are marketing prepaid phone cards in the United States, adding up to an estimated $1.1 billion domestic market. And Global Telecommunications Solutions Inc., based in Northeast Philadelphia, was one of the first companies to begin mining that market.

Founded in 1992, Global Telecommunications has been a pioneer in the introduction of phone cards in the United States and was one of the industry's first full-scale companies devoted solely to the production and marketing of prepaid phone cards.

"You could say we're the 'father of phone cards,'" said Gary J. Wasserson, Global Telecommunications' chief executive officer. "We were the first in three areas: the traditional card sold in drugstores and supermarkets, the promotional card used by corporations and organizations, and, most importantly, the interactive card, which combines interactivity with promotion."

A publicly held company, Global …