Walkie-talkies (formally called handheld transceivers) are portable two-way communication devices. Each one has a speaker, microphone, and antenna; multiple walkie-talkies will all use the same frequency. One can transmit at a time, but all can receive to that transmission simultaneously. Walkie-talkies were originally developed by American engineers during World War II, but have since become widely available for commercial and personal use.
