Jacquesm has it right, just an ordinary radio. There was a reason the brick-sized Motorola DynaTAC had only a 30 minute talk time, and it wasn't that the batter

Jacquesm has it right, just an ordinary radio. There was a reason the brick-sized Motorola DynaTAC had only a 30 minute talk time, and it wasn't that the battery was small. Thus the popularity of the carphone, as noted elsewhere. It's hard to get a straight up comparison of transmission strength, because it's highly dependent on how close you are to the tower, but even if you assume max power all the time, it's about an order of magnitude less on digital.