A walkie-talkie, or handheld transceiver, is a hand-held, portable, two-way radio transceiver. Handheld two-way radios were developed by the military from backpack radios carried by a soldier in an infantry squad to keep the squad in contact with their commanders during World War II. Walkie-talkies were first used for infantry and then spread to public usage.
Walkie-talkies usually resemble a telephone handset, with a speaker built on one end and a microphone on the other and an antenna mounted on the top. They are held up to the face to talk. Multiple walkie-talkies use a single radio channel, and only one radio on the channel can transmit at a time, although any number of people can listen. The transceiver is normally in receive mode; when the user wants to talk they must press a "push-to-talk" (PTT) button that turns off the receiver and turns on the transmitter. Smaller versions of this device are also very popular among young children.