page_title: Two-way radio
hierarchical_section_title: Two-way radio
caption_attribution_description: English: A collection of walkie-talkies, handheld portable two-way radios for recreational use. From left: Motorola FRS radio, purchased in 2002, which operates on the Family Radio Service band. Motorola dual band walkie-talkie, purchased in 2004, which can operate on either the FRS or the General Mobile Radio Service (GMRS) channels. On both these radios, the antenna is permanently attached, as required by FCC regulations for FRS gear. Early 1980s amateur radio transceiver for the 2 meter (144 MHz) band, complete with external speaker-mike, and DTMF keypad for remote repeater control and phone patch operation. Smaller amateur transciever for the 2 meter (144 MHz) and 70 cm (428 MHz) bands. Although similar in size to the smaller FRS units, it is much more versatile, has a higher transmit power, and can transmit on any of several hundred frequencies in two Amateur radio bands. A 1960s vintage toy walkie-talkie operating in the 27 MHz Citizens' Band; its 900 mm (36 inch)whip antenna is partly extended. This unit has a superheterodyne receiver, and 10 transistors. A mid-1980's toy walkie-talkie operating at very low power in the 49 MHz band, with a Morse code key and the Morse code printed on the case. This unit has only 4 transistors and no volume control or squelch. In addition, rather than the telescoping whip antenna common on earlier models, this unit has a rubber duck antenna, which is thought to be more robust and less dangerous to the user if broken, and has replaced telescoping antennas in virtually all children's two-way radio units. Commercial and emergency services walkie-talkies may be similar in size to the amateur units shown here, but generally have much better battery life, more rugged construction, and simpler controls, often restricting operation to only one or a few pre-programmed channels. In addition, many have ruggedizing features such as waterproofing (especially for outdoors and marine use) and intrinsically safe design for use in fire-prone industrial environments. The two older walkie-talkies on the right use only discrete transistors; all the more recent ones shown here use microprocessors and integrated circuits for most of their functions.
context_page_description: A two-way radio is a radio that can both transmit and receive radio waves, unlike a broadcast receiver which only receives content. It is an audio transceiver, a transmitter and receiver in one unit, used for bidirectional person-to-person voice communication with other users with similar radios. Two-way radios are available in stationary, mobile, and hand-held portable models. Hand-held two-way radios are often called walkie-talkies, handie-talkies or hand-helds. Two-way radios are used by groups of geographically separated people who need to keep in continuous voice communication, such as aircraft pilots and air traffic controllers, ship captains and harbormasters, emergency services personnel like firemen, policemen, and ambulance paramedics, taxi and delivery services, soldiers and military units, fast food and warehouse employees, and radio amateurs.
  Two-way radio systems usually use a single radio channel and operate in a half-duplex mode: only one user on the channel can transmit at a time, so users in a user group must take turns talking. The radio is normally in receive mode so the user can hear all other transmissions on the channel.
context_section_description: A two-way radio is a radio that can both transmit and receive radio waves (a transceiver), unlike a broadcast receiver which only receives content. It is an audio (sound) transceiver, a transmitter and receiver in one unit, used for bidirectional person-to-person voice communication with other users with similar radios. Two-way radios are available in stationary (base station), mobile (installed in vehicles), and hand-held portable models. Hand-held two-way radios are often called walkie-talkies, handie-talkies or hand-helds.  Two-way radios are used by groups of geographically separated people who need to keep in continuous voice communication, such as aircraft pilots and air traffic controllers, ship captains and harbormasters, emergency services personnel like firemen, policemen, and ambulance paramedics, taxi and delivery services, soldiers and military units, fast food and warehouse employees, and radio amateurs.
  Two-way radio systems usually use a single radio channel and operate in a half-duplex mode: only one user on the channel can transmit at a time, so users in a user group must take turns talking.  The radio is normally in receive mode so the user can hear all other transmissions on the channel.  When the user wants to talk he presses a "push-to-talk" button, which turns off the receiver and turns on the transmitter; when he releases the button the receiver is activated again.  Multiple channels are provided so separate user groups can communicate in the same area without interfering with each other. Other two-way radio systems operate in full-duplex mode, in which both parties can talk simultaneously.  This requires either two separate radio channels or channel sharing methods such as time division duplex (TDD) to carry the two directions of the conversation simultaneously on a single radio frequency.  A cell phone is an example of a full-duplex two-way radio. During a phone call, the phone communicates with the cell tower over two radio channels; an incoming one to carry the remote party's voice to the user, and an outgoing one to carry the user's voice to the remote party.
caption: A variety of portable handheld two-way radios for private use.
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