As a clerk bags her groceries, Nancy Piech slides a small piece of plastic through a black machine in front of her on the checkout counter. It's the same automatic-teller machine (ATM) card she uses at her bank to get instant cash and make deposits.
Unlike a check or credit card which offers the luxury of time before the payment goes through, this debit card electronically transfers the funds at once from Mrs. Piech's checking account to that of this Hy-Vee Food Store in West Des Moines.
''It took me a while to get used to it, but now I like it very much,'' says Mrs. Piech, who is spared the nuisance and cost of writing a check or having a credit card cleared.
As yet, most debit card testing is going on in food stores and gas stations. Exxon gas stations in both Houston and Phoenix, for instance, accept certain ATM cards. And in Florida where a statewide project is under way, some 200 Mobil Oil stations and a number of small merchants selling everything from mufflers to magic goods have been accepting ATM cards on a permanent basis since Oct. 1.
''It's the hot item these days,'' agrees Catherine Brown, education director of the Electronic Funds Transfer Association (EFTA). ''The potential transaction volume for this kind of (debit card) business is very high.''
Yet by most objective accounts the debit card has moved rather slowly onto the retail scene. The technology is expensive, and competitive bankers and retailers have found it hard to agree on a shared electronic network.
Iowa, where the Hy-Vee use of ATM cards is in its fourth year, is one of the few states where all financial institutions agreed early to join in a single network - ITS Inc. Most grocery stores in the United States continue to rely on cash and checks for the bulk of customer purchases.
Unlike most credit cards, the card clears automatically (''you don't have to depend any more on the cosmetics of the card to know whether it's accepted,'' says Mr. Dooley) and the merchant gets his money instantly.
But there is a disadvantage in the debit card for the consumer who likes the free float offered by check or credit card. To counter that drawback, companies such as Exxon offer a cash discount to make debit-card use more attractive.
Still, Darrell Vore, manager of the West Des Moines Hy-Vee store, says he doubts debit cards will prosper ''unless bankers start charging customers what it costs them to process checks.''
And most credit experts say they do not think that American shoppers will one day use only one piece of plastic for all their purchases and banking transactions. Even having one debit card is considered unlikely.
Although an estimated 600 million credit cards are used by 70 percent of America's families, according to the Federal Reserve Board, the average number of credit cards in each household is slightly down these days. Recently imposed annual fees on bank cards are considered a key factor.
But EFTA's Sharon Brown says she doesn't think the clutch of credit cards most people carry will fall below a certain ''critical mass.''
''The hope is there'll be a card that can be used as a credit or debit card just for simplification's sake,'' Ms. Brown says. ''The technology is possible, but the consumer wouldn't stand for it. Retailers would love to have it, but they're not going to push consumers anywhere they (the consumers) don't want to go.''