How Does a Two-Way Radio Work?

Radio Waves
A 2 way radio is simply a regular radio that is equipped with a transmitter and receives a signal from only one other transmitter.
Radio waves work by converting data (of any kind, but in this case sound) into a sine wave. A sine wave is a form electronic signal that is based on oscillating electrical current. (To oscillate means to change between two points.) A sine wave moves repeatedly between two points of high and low voltage; this change is known as the amplitude of the wave.
These electrical currents are generated by just one object, but they will naturally affect any conductive material in their vicinity, because they cause electrons to move in all directions. Transmission is the process of electrically boosting this occurrence.
Encoding Information
A sine wave does not carry information on its own. For sound data to be transmitted, it needs to be converted into a sine wave itself, then attached to a “signal” sine wave. This can be done by altering the amplitude– hence the term amplitude modulation, or AM, as in AM radio. A two-way talk radio uses amplitude modulation.
Carrier Signals and Information Signals
The rate at which a sine wave oscillates is known as the frequency of the wave. The sine wave of each data stream has its own frequency, which enables us to tell one wave from another.
To locate a particular signal that is being transmitted, any signal-receiving device must be calibrated to pick up a particular speed of sine wave. A two-way radio will usually only pick up one frequency–namely, the one coming from its partner or partners. The radio is also equipped with a tuner, which filters out all other signals.
A standard two-way radio can send and receive signals, but not at the same time. A cellular phone, however, is merely a form of two-way radio that can.
Microphone
All two-way radios contain microphones. A microphone is a device that converts sound into electrical patterns, which can then be sent over the radio. The microphone does this using the vibrational energy all sound produces. There is a variety of ways in which microphones do this, but all involve some type of internal device that is physically vibrated by the sound that reaches it.
Speaker
2 way radios also contain speakers. A speaker works according to a similar principle as a microphone, but in this case, the electrical patterns are being converted into sound waves, then amplified. The speaker picks up these signals from radio broadcasts and transforms them into amplified vibrations, which the ear and brain translate into sound.