A two-way radio, or transceiver, is a radio device that can both transmit or receive audio broadcasts. Virtually everyone has used some type of two-way radio in their lifetime. The types of devices that classify as two-way radios range from simple "walkie-talkies" or even baby monitors to cell-phones used in everyday life.
Two-way radios generally come in two different styles, simplex and duplex. A simplex two-way radio is classified as one that uses one channel to relay messages. What this means is that only one person in the conversation can speak and be heard at any one time. The most common type of simplex two-way radio is a hand-held radio, or walkie-talkie, which usually features a “push-to-talk” button to instigate transmissions from one unit to another. Meanwhile, a duplex two-way radio uses two different radio frequencies simultaneously, creating the ability to carry-on a continuous conversation. Common examples of these types of two-way radios are products many people use in their everyday lives, such as cordless or cellular telephones.
Both types of two-way radio have the ability to send data as well as audio with differing ability and limitations. Duplex two-way radio systems can transmit data from one point to another in real time while simplex systems have a time lag. There have also been examples of radios that can utilize both simplex and duplex systems. Meaning that two radios can communicate simultaneously when they are within a certain range of each other, but can also communicate through a single channel when out of range. A two-way radio with this ability is often referred to as a talk around device, direct device, or car-to-car device.
Some two-ways use analog technology while others broadcast digitally, and as always, there are advantages and disadvantages of both. With analog there is better ability to communicate when signals are weak or noisy but, as mentioned above, only one side of a conversation can be held at one time. On the other hand, digital systems provide simultaneous communication and the ability to send more information than analog, such as text messaging. However, digital devices, such as cell phones, all have to be designed to a certain standard, are more expensive, and become obsolete quickly.