Compared to a simplex CB radio in which both transmitters use the same frequency and only one party can talk at a time, a cell phone is a duplex device, and so it uses one frequency for talking and a second, separate frequency for listening. That s why both parties can talk at the same time. In addition, a cell phone can communicate on 1664 channels, though a CB radio had only 40 channels. Only one party can talk at a time. In duplex radio the two transmitters use different frequencies, so both parties can talk at the same time.
Cell phones are duplex.
The cellular system is based on the concept that a city can be chopped up into small cells. The carrier chops up an area such as a city into cells, which are normally thought of as hexagons on a big hexagonal grid, like below. Each cell is typically sized at about 10 square miles. And cell phones operate within cells which give cell phones their incredible range, and they can switch cells as they move around. The standard established a range of frequencies between 824 megahertz and 894 megahertz for analog cell phones.