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Digital Private Mobile Radio
dPMR or digital private mobile radio, is a common air interface for digital mobile communications. dPMR is an open, non-proprietary standard that was developed by the European Telecommunications Standards Institute (ETSI) and published under the reference ETSI TS 102 658. A simplified version of the dPMR protocol intended for licence-free applications was also published by ETSI under the reference TS 102 490. dPMR is very similar to NXDN protocol implementation by Kenwood and Icom; both now offer dual-standard equipment (July 2013). Specifications *Access method: FDMA *Transmission rate: 4,800 bit/s *Modulation: four-level FSK What is significant is that dPMR achieves all this in a 6.25 kHz channel. Because the emission mask is so tight, two 6.25 kHz dPMR signals can be used next to each other within a 12.5 kHz channel without causing interference to each other or adjacent channels. Compliance with EN301 166 at 6.25 kHz for current equipment provides some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Private Mobile Radio
Professional mobile radio (also known as private mobile radio (PMR) in the UK) are person-to-person two-way radio voice communications systems which use portable, mobile, base station, and dispatch console radios. PMR radio systems are based on such standards as MPT-1327, TETRA, APCO 25, and DMR which are designed for dedicated use by specific organizations, or standards such as NXDN intended for general commercial use. These systems are used by police, fire, ambulance, and emergency services, and by commercial firms such as taxis and delivery services. Most systems are half-duplex, in which multiple radios share a common radio channel, and only one can transmit at a time. Transceivers are normally in receive mode, the user presses a push-to-talk button on his microphone when he wants to talk, which turns on his transmitter and turns off his receiver. They use channels in the VHF and UHF bands, giving them a limited range, usually depending on terrain. Output power is typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AMBE+2
An ambe, in anatomy, is a superficial jutting out of a bone. Ambe is also the name of an old surgical instrument, made famous by Hippocrates, for reducing dislocations of the shoulder, so called because its extremity projects like the prominence of a rock. It was described in the Philosophical Transactions of the Royal Society as making a sufficient extension and counter-extension to guide the dislocated bone back into joint.John Martyn Iain David McGeachy (11 September 1948 – 29 January 2009), known professionally as John Martyn, was a Scottish singer-songwriter and guitarist. Over a 40-year career, he released 23 studio albums, and received frequent critical acclaim. ..., '' The Philosophical Transactions'' (From the Year 1732, to the Year 1744), Vol. 9, p. 258. References * ;Attribution External linksHippocrates' written description of the tool and its use History of surgery Musculoskeletal system {{treatment-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MPT-1327
MPT 1327 is an industry standard for trunked radio communications networks. First published in January 1988 by the British Radiocommunications Agency, and is primarily used in the United Kingdom, Europe, South Africa, New Zealand, Australia and even China. Many countries had their own version of numbering/user interface, including MPT1343 in the UK, Chekker (Regionet 43) in Germany, 3RP (CNET2424) in France, Multiax in Australia, and Gong An in China. MPT systems are still being built in many areas of the world, due to their cost-effectiveness. Digital alternatives The TETRA trunked radio standard was developed by the European Telecommunications Standards Institute (ETSI), as a digital alternative to analogue trunked systems. However, TETRA, with its enhanced encryption capability, has developed into a higher tier (public safety) product, currently mainly used by governments, some larger airports and government-owned utilities. DMR (digital mobile radio), and dPMR ( d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Mobile Radio
Digital mobile radio (DMR) is a specification for commercial products so they can interoperate. It is defined by a standard created by the European Telecommunications Standards Institute (ETSI), and is designed to be low-cost and easy to use. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discrete 6.25 kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel. DMR was designed with three tiers. DMR tiers I and II (conventional) were first published in 2005, and DMR III (Trunked version) was published in 2012, with manufacturers producing products within a few years of each publication. The primary goal of the standard is to specify a digital system with low complexity, low cost and interoperability across brands, so radio communications purchasers a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Communications Committee
The European Conference of Postal and Telecommunications Administrations (CEPT) was established on June 26, 1959, by nineteen European states in Montreux, Switzerland, as a coordinating body for European state telecommunications and postal organizations. The acronym comes from the French version of its name ''Conférence européenne des administrations des postes et des télécommunications''. CEPT was responsible for the creation of the European Telecommunications Standards Institute (ETSI) in 1988. CEPT is organised into three main components: * Electronic Communications Committee (ECC) - responsible for radiocommunications and telecommunications matters and formed by the merger of ECTRA (European Committee for Telecommunications Regulatory Affairs) and ERC (European Radiocommunications Committee) in September 2001 **The permanent secretariat of the ECC is the European Communications Office (ECO) * European Committee for Postal Regulation (CERP, after the French ''"Comi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PMR446
PMR446 (Private Mobile Radio, 446 MHz) is a licence exempt service in the UHF radio frequency band and is available for business and personal use in most countries throughout the European Union. PMR446 is typically used for small-site, same-building and line of sight outdoor activities. Equipment used ranges from consumer-grade to professional quality walkie-talkies (similar to those used for FRS/GMRS in the United States and Canada). Depending on surrounding terrain range can vary from a few hundred metres (in a city) to a few kilometres (flat countryside) to many kilometres from high ground. Historically, analogue FM is used but a digital voice mode has been available in radios conforming to digital private mobile radio (dPMR446) and digital mobile radio (DMR Tier 1) standards designed by ETSI. Originally 8 channels were available in analogue mode but this has now been increased to 16 channels. Typically PMR446 is used for both recreational and business use, addition ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RALCWI
A vocoder (, a portmanteau of ''voice'' and ''encoder'') is a category of speech coding that analyzes and synthesizes the human voice signal for audio data compression, multiplexing, voice encryption or voice transformation. The vocoder was invented in 1938 by Homer Dudley at Bell Labs as a means of synthesizing human speech. This work was developed into the channel vocoder which was used as a voice codec for telecommunications for speech coding to conserve bandwidth in transmission. By encrypting the control signals, voice transmission can be secured against interception. Its primary use in this fashion is for secure radio communication. The advantage of this method of encryption is that none of the original signal is sent, only envelopes of the bandpass filters. The receiving unit needs to be set up in the same filter configuration to re-synthesize a version of the original signal spectrum. The vocoder has also been used extensively as an electronic musical instrument. The d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency-shift Keying
Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier signal. The technology is used for communication systems such as telemetry, weather balloon radiosondes, caller ID, garage door openers, and low frequency radio transmission in the VLF and ELF bands. The simplest FSK is binary FSK (BFSK). BFSK uses a pair of discrete frequencies to transmit binary (0s and 1s) information. With this scheme, the 1 is called the mark frequency and the 0 is called the space frequency. Modulating and demodulating Reference implementations of FSK modems exist and are documented in detail. The demodulation of a binary FSK signal can be done using the Goertzel algorithm very efficiently, even on low-power microcontrollers. Variations Multiple frequency-shift keying Continuous-phase frequency-shift keying In principle FSK can be implemented by using completely independent free-running oscillat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Air Interface
Project 25 (P25 or APCO-25) is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. P25 radios are a direct replacement for analog UHF (typically FM) radios, but add the ability to transfer data as well as voice, allowing for more natural implementations of encryption and text messaging. P25 radios are commonly implemented by dispatch organizations, such as police, fire, ambulance and emergency rescue service, using vehicle-mounted radios combined with repeaters and handheld walkie-talkie use. Starting around 2012, products became available with the newer phase 2 modulation protocol, the older protocol known as P25 became P25 phase 1. P25 phase 2 products use the more advanced AMBE2+ vocoder, which allows audio to pass through a more compressed bitstream and provides two TDMA voice chann ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FDMA
Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing the bandwidth of the channel into separate non-overlapping frequency sub-channels and allocating each sub-channel to a separate user. Users can send data through a subchannel by modulating it on a carrier wave at the subchannel's frequency. It is used in satellite communication systems and telephone trunklines. FDMA splits the total bandwidth into multiple channels. Each ground station on the earth is allocated a particular frequency group (or a range of frequencies). Within each group, the ground station can allocate different frequencies to individual channels, which are used by different stations connected to that ground station. Before the transmission begins, the transmitting ground station looks for an empty channel within the freq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Icom Incorporated
is a Japanese manufacturer of radio transmitting and receiving equipment, founded in 1954 by Tokuzo Inoue with the company's original name being "Inoue". Its products now include equipment for radio amateurs, pilots, maritime applications, land mobile professional applications and radio scanner enthusiasts. Its headquarters are in Osaka, Japan, with branch offices in the United States (in Kirkland, Washington), Canada (in Delta, British Columbia), Australia (Melbourne, Victoria), New Zealand (Auckland), the United Kingdom (Kent, England), France (Toulouse), Germany (Bad Soden), Spain (Barcelona) and the People's Republic of China (Beijing). Protocols IDAS IDAS is Icom's implementation of the NXDN protocol for two-way digital radio products intended for commercial Private Land Mobile Radio (PLMR) and low-end public safety communications systems. NXDN is a Common Air Interface (CAI) technical standard for mobile communications. It was developed jointly by Icom and Kenwood Corpor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
