When AT& T orders you to "know the code," it's referring to its 800 number for collect calls. But there are codes it would prefer you didn't know -- codes that would give you access to cheaper long-distance carriers, even if AT& T is your primary service. "The industry knows a dirty little secret," says Robert Pokress, founder of MediaCom Corp., a manufacturer of PC-based telephony software in Bedford, Mass. "You don't have to be locked into one long-distance company."

Pokress developed the Phone-Miser system so that small companies and individuals (who can't afford to pay someone to worry about phone issues) could take advantage of the peculiar design of the telephone infrastructure -- lines piggybacking upon lines -- to find the cheapest fare for long-distance calls. The system consists of a software program and a hardware device that plugs into the parallel port of a PC. Each time you dial a long-distance number, Phone-Miser "listens" and routes the call, using special codes to access the cheapest carrier.

Though the product won't be available until July, MediaCom is accepting orders for it at its Web site (www.phonemiser.com). Phone-Miser costs just under $100, but Pokress estimates it could save small businesses more than 50% on their phone bills.