Working Knowledge; May 2000; Scientific American Magazine; by Holloway; 2 Page(s)

Full-service gas stations are all but extinct in the U.S. Today about 90 percent of gasoline purchases-some 16 billion transactions a year, according to the American Petroleum Institute in Washington, D.C.-are made by customers willing to pump for themselves. Self-serve technology has changed relatively little since 1947, when two Californians seem to have come up with the idea almost simultaneously. Although self-serve stations saved customers money (the first ones charged five cents less per gallon), they were thought to be a fad, something Americans would eventually tire of. But by the 1970s they were clearly here to stay. New Jersey and Oregon, however, still allow only station attendants to pump gas.

Today self-service is largely controlled by electronics. As Matthew C. Schuessler of the dispenser manufacturer Marconi Commerce Systems in Greensboro, N.C., explains, when a customer lifts the pump handle or pushes a button on the dispenser, a signal goes to the pump controller board in the upper part of the dispenser. The board resets the display counter to zero, informs the station operator that there is a customer and engages the hydraulic interface board, through which it regulates the flow of gas from the underground tank. (The electronics and hydraulics of dispensers are carefully separated by an air gap or an epoxylike material to reduce the risk of sparking an explosion.)