Technically a cell phone is a type of two way radio, although it is not generally what one thinks of when the term two way radio comes up in conversation. The first application of two way radios was in the early 1900's for ships and police cars.

Ships at sea could get lost easily and were able to call for help with the use of a two way radio. This way, they could be located and someone could come to their rescue.

The original police radio was very large (took up the entire back seat), although it was better than stopping to use a public phone to report back (which was the method used prior to the advent of two way radios in police cars). Naturally, two way communications not only back to the police station but from one police car to another had strong advantages.

Today there are a wide variety of two way radio applications, a cell phone being one of them. CB radios used by truckers and other traveling professions are one example. Another example is the walkie-talkies generally used by children.

There are many different types of two way radios, from a technical standpoint. One is a called a conventional two way radio. This uses fixed radio frequency channels for its transmission and receipt of signals. With a conventional two way radio, the frequency used is selected by the person sending the message.

Another two way radio is called a trunked radio system, which is more computerized than some of the others. Instead of using one carrier frequency for the communication, a trunked radio system selects a radio channel on its own from the ones available.

For example, Nextel has a phone that uses trunked radio technology, which allows people to talk instantly without actually dialing a phone number to make a call. This is handy in work situations, or situations where any immediate communication is required.

Another type of two way radio is, again, the type we call a walkie-talkie. Although there are models intended for children, adults can use professional two way radios of this kind to keep in touch during trips or even for professional use. The adult type models don't look as much like toys necessarily, but are compact enough to easily carry with you in your pocket.

Constructions workers, for instance, may benefit from the use of two way radios. When working on a building or road, it is very important that the personnel in all areas of the project be able to communicate.

A two way radio has advantages over cell phones and pagers. Cell phones require a phone call to be made, which requires more time, for one thing. It is also probably quite difficult in an emergency or in a dark place (such as miners in a dark mine) to dial a phone number. Locating the two way radio in your pocket and pressing one button is much more realistic in those scenarios.

A pager is also quite impractical if immediate communication is needed. There are instances where a pager can be helpful, but many where two way radio is superior.