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Two-way Radio
A two-way radio is a radio that can do both transmit and receive a signal (a transceiver), unlike a broadcast receiver which only receives content. A two-way radio (transceiver) allows the operator to have a conversation with other similar radios operating on the same radio frequency (channel). Two-way radios are available in mobile, stationary base and hand-held portable configurations. Hand-held radios are often called walkie-talkies, handie-talkies or hand-helds. Two-way radio systems usually operate in a half-duplex mode; that is, the operator can talk, or he can listen, but not at the same time. A push-to-talk or Press To Transmit button activates the transmitter; when it is released the receiver is active [...More Info...] [...Related Items...] |
Cellular Telephone
A mobile phone, known as a cell phone in North America, is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area. The radio frequency link establishes a connection to the switching systems of a mobile phone operator, which provides access to the public switched telephone network (PSTN). Modern mobile telephone services use a cellular network architecture, and, therefore, mobile telephones are called cellular telephones or cell phones, in North America. In addition to telephony, 2000s-era mobile phones support a variety of other services, such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, video games, and digital photography [...More Info...] [...Related Items...] |
Vacuum Tubes
In electronics, a vacuum tube, an electron tube, or just a tube (North America), or valve (Britain and some other regions) is a device that controls electric current between electrodes in an evacuated container. Vacuum tubes mostly rely on thermionic emission of electrons from a hot filament or a heated cathode. This type is called a thermionic tube or thermionic valve. A phototube, however, achieves electron emission through the photoelectric effect. Not all electronic circuit valves/electron tubes are vacuum tubes (evacuated); gas-filled tubes are similar devices containing a gas, typically at low pressure, which exploit phenomena related to electric discharge in gases, usually without a heater. The simplest vacuum tube, the diode, contains only a heater, a heated electron-emitting cathode (the filament itself acts as the cathode in some diodes), and a plate (anode) [...More Info...] [...Related Items...] |
Cat's-whisker Detector
A crystal detector is an electronic component used to rectify radio frequency alternating current. The "asymmetric conduction" of crystals was discovered in 1874 by Karl Ferdinand Braun, and the first crystal detectors were used to receive radio waves by Braun and Jagadish Chandra Bose in 1894, and improved around 1904 by radio researchers such as Henry H. C. Dunwoody and G. W. Pickard, this device was used as the detector in early crystal radios, from the early twentieth century through World War II, and gave this type of radio receiver its name. Crystal radios were the most popular type of radio until the mid 1920s [...More Info...] [...Related Items...] |
Whip Antenna
A whip antenna is an antenna consisting of a straight flexible wire or rod. The bottom end of the whip is connected to the radio receiver or transmitter. The antenna is designed to be flexible so that it does not break easily, and the name is derived from the whip-like motion that it exhibits when disturbed. Whip antennas for portable radios are often made of a series of interlocking telescoping metal tubes, so they can be retracted when not in use. Longer ones, made for mounting on vehicles and structures, are made of a flexible fiberglass rod around a wire core and can be up to 35 ft (10 m) long. The length of the whip antenna is determined by the wavelength of the radio waves it is used with. The most common type is the quarter-wave whip, which is approximately one-quarter of a wavelength long. Whips are the most common type of monopole antenna, and are used in the higher frequency HF, VHF and UHF radio bands [...More Info...] [...Related Items...] |
United States Marine Corps
The United States Marine Corps (USMC), also known as the United States Marines, is a branch of the United States Armed Forces responsible for conducting amphibious operations with the United States Navy. The U.S. Marine Corps is one of the four armed service branches in the U.S. Department of Defense (DoD) and one of the seven uniformed services of the United States. The Marine Corps has been a component of the U.S. Department of the Navy since 30 June 1834, working closely with naval forces. The USMC operates installations on land and aboard sea-going amphibious warfare ships around the world [...More Info...] [...Related Items...] |
Squad
In military terminology, a squad or squadron is a sub-subunit led by a non-commissioned officer that is subordinate to an infantry platoon. In countries following the British Army tradition (Australian Army, Canadian Army, and others), this organization is referred to as a section [...More Info...] [...Related Items...] |
United States Army
The United States Army (USA) is the land warfare service branch of the United States Armed Forces. It is one of the seven uniformed services of the United States and is designated as the Army of the United States in the United States Constitution, Article 2, Section 2, Clause 1 and United States Code, Title 10, Subtitle B, Chapter 301, Section 3001. As the oldest and most senior branch of the U.S. military in order of precedence, the modern U.S [...More Info...] [...Related Items...] |
Amateur Radio
Amateur radio (also called ham radio) describes the use of radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communication. The term "amateur" is used to specify "a duly authorised person interested in radioelectric practice with a purely personal aim and without pecuniary interest;" (either direct monetary or other similar reward) and to differentiate it from commercial broadcasting, public safety (such as police and fire), or professional two-way radio services (such as maritime, aviation, taxis, etc.). The amateur radio service (amateur service and amateur-satellite service) is established by the International Telecommunication Union (ITU) through the Radio Regulations [...More Info...] [...Related Items...] |
Civil Defense
Civil defense, civil defence (see spelling differences) or civil protection is an effort to protect the citizens of a state (generally non-combatants) from military attacks and natural disasters. It uses the principles of emergency operations: prevention, mitigation, preparation, response, or emergency evacuation and recovery. Programs of this sort were initially discussed at least as early as the 1920s and were implemented in some countries during the 1930s as the threat of war and aerial bombardment grew. It became widespread after the threat of nuclear weapons was realized. Since the end of the Cold War, the focus of civil defense has largely shifted from military attack to emergencies and disasters in general [...More Info...] [...Related Items...] |
Trunked Radio System
A trunked radio system is two-way radio system that uses a control channel to automatically direct radio traffic. Two-way radio systems are either trunked or conventional, where conventional is manually directed by the radio user. Trunking is a more automated and complex radio system, but provides the benefits of less user intervention to operate the radio and greater spectral efficiency with large numbers of users. Instead of assigning, for example, a radio channel to one particular organization at a time, users are instead assigned to a logical grouping, a "talkgroup". When any user in that group wishes to converse with another user in the talkgroup, a vacant radio channel is found automatically by the system and the conversation takes place on that channel. Many unrelated conversations can occur on a channel, making use of the otherwise idle time between conversations. Each radio transceiver contains a microcomputer to control it [...More Info...] [...Related Items...] |
Battle Of Noemfoor
The Battle of Noemfoor was a battle of World War II that took place on the island of Noemfoor, in Dutch New Guinea, between 2 July and 31 August 1944 [...More Info...] [...Related Items...] |
Base Station
Base station (or base radio station) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a "land station in the land mobile service." The term is used in the context of mobile telephony, wireless computer networking and other wireless communications and in land surveying. In surveying, it is a GPS receiver at a known position, while in wireless communications it is a transceiver connecting a number of other devices to one another and/or to a wider area. In mobile telephony, it provides the connection between mobile phones and the wider telephone network. In a computer network, it is a transceiver acting as a router for computers in the network, possibly connecting them to a local area network and/or the internet [...More Info...] [...Related Items...] |
