A walkie-talkie (more formally known as a handheld transceiver) is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola. Similar designs were created for other armed forces, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work. Major characteristics include a half-duplex channel (only one radio transmits at a time, though any number can listen)