A walkie-talkie is a portable, bi-directional radio transceiver, first developed for military use. Major characteristics include a half-duplex (only one of receive or transmit at a time) channel and a push-to-talk switch that starts transmission. The typical physical format looks like a telephone handset, possibly slightly larger but still a single unit, with an antenna sticking out of the top.
Hand-held transceivers became valuable communication tools for police, emergency services, and industrial and commercial users, using frequencies assigned for these services.
Low-power versions, exempt from licence requirements, are also popular children's toys. Prior to the change of CB radio from licensed to un-licensed status, the typical toy walkie-talkie available in retail stores in North America was limited to 100 milliwatts of power on transmit and the 27 MHz citizens' band channels. Other toy walkie-talkies operate in the 49 MHZ band shared with cordless phones and baby monitors; typically these devices are very crude electronically and may lack even a volume control, though they may have elaborate packaging.
The first radio receiver/transmitter to be nick-named "Walkie-Talkie" was the Motorola SCR-300 created by an engineering team in 1940 at the Galvin Manufacturing Company consisting of Dan Noble, who conceived of the design using FM technology, Henryk Magnuski who was the principal RF engineer, Marion Bond, Lloyd Morris, and Bill Vogel. Motorola also produced the SCR-536 radio during the war, and it was called the "Handie-Talkie" (HT).
Al Gross also worked on the early technology behind the walkie-talkie between 1934 and 1941, and is sometimes said to actually have invented it.
The personal walkie-talkie has now become popular again with the Family Radio Service. FRS operates in the GMRS band, which is also used for business walkie-talkies and mobile radios. While FRS walkie-talkies are popular toys, they are also a useful communication tool for business and personal use.