Business travelers who leave cellular phones behind because of high roaming charges have found that renting is hardly a better deal. Because bills for most hired cellular phones are calculated according to the time in use -- not according to the distance of the call -- many a lessee who's been talking to the next town has been shocked on return by blanket charges calculated at the same rate as if the call had been made to the next hemisphere.

Now, however, a new computer chip embedded inside rental phones records not only each call's duration but also its destination. When the phone is returned, the data are downloaded into the rental agent's computer, which prints out a detailed bill on the spot -- more useful for executives who file line-item expense reports.

The technology for the system -- called the TRAC System -- was developed by Telemac Cellular, in Danville, Calif. Panasonic and Murata already are delivering phones with TRAC installed. Some of the first systems were purchased by American Cellular Rental (ACR), based in Fort Lauderdale, Fla., which rents them out in affiliation with Alamo car-rental agencies. ACR also has installed modules in a fleet of Palm Beach limousines, and equips trade and professional functions with handheld units. ACR is unrolling TRAC phone-rental outlets in other states; expect to find them soon in New Jersey, Pennsylvania, and Texas.

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