A two-way radio is a radio that can both transmit and receive, unlike a broadcast receiver which only receives content. A two-way radio allows the operator to have a conversation with other similar radios operating on the same radio frequency. Two-way radios are available in mobile, stationary base and hand-held portable configurations. Hand-held radios are often called walkie-talkies, handie-talkies, or just hand-helds.
Two-way radio systems usually operate in a half-duplex mode; that is, the operator can talk, or he can listen, but not at the same time. A push-to-talk or Press To Transmit button activates the transmitter; when it is released the receiver is active. A mobile phone or cellular telephone is an example of a two-way radio that both transmits and receives at the same time. It uses two different radio frequencies to carry the two directions of the conversation simultaneously.


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