TETRA system for the Riga Municipal Police / DAN Communications". www.dan.lv . Retrieved 2020-06-21. The downlink (i.e., the output of the base station) is normally a continuous transmission consisting of either specific communications with mobile(s), synchronisation or other general broadcasts. All slots are usually filled with a burst even if idle (continuous mode). Although the system uses 18 frames per second only 17 of these are used for traffic channels, with the 18th frame reserved for signalling, Short Data Service messages (like SMS in GSM) or synchronisation. The frame structure in TETRA (17.65 frames per second), consists of 18,000 symbols/s; 255 symbols/slot; 4 slots/frame, and is the cause of the perceived "amplitude modulation" at 17Hz and is especially apparent in mobiles/portables which only transmit on one slot/4. They use the remaining three slots to switch frequency to receive a burst from the base station two slots later and then return to their transmit frequency ( TDMA). Rapid deployment (transportable) network solutions are available for disaster relief and temporary capacity provision.

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TETRA provides for authentication of terminals towards infrastructure and vice versa. For protection against eavesdropping, air interface encryption and end-to-end encryption is available.Allow any given agent while in exercise, to exploit any given radio terminal without materiel constraint. Project 25 and TETRA are utilised for the public safety Radio network and Private Sector Radio network worldwide however, it has some differences in technical features and capacities. [18] [19] [20] Up to 7.2kbit/s per timeslot, in the case of point-to-point connections, and 3.5kbit/s per timeslot in case of IP encapsulation. TETRA Mobile Stations (MS) can communicate direct-mode operation (DMO) or using trunked-mode operation (TMO) using switching and management infrastructure (SwMI) made of TETRA base stations (TBS). As well as allowing direct communications in situations where network coverage is not available, DMO also includes the possibility of using a sequence of one or more TETRA terminals as relays. This functionality is called DMO gateway (from DMO to TMO) or DMO repeater (from DMO to DMO). In emergency situations this feature allows direct communications underground or in areas of bad coverage. cite web|url= http://www.artevea.com/casestudies-detail.php?type=case&id=11 |title=TETRA: Artevea Digital Limited: Digital Radio Communication |publisher=Artevea.com |date|access-date=2012-03-28}}

Ofcom Mobile coverage, technical and planning advice - Ofcom

Now just what happens to the citizens of a country that decides to install masts all across the country, in or near every village and city, broadcasting a high-power and high-amplitude wave pattern which is in the middle of our waking-state brainwave rhythm? The simple answer is that a large portion of that population will suffer badly from inadequate and disturbed sleep patterns, at the very least. But there are many other symptoms that arise. As Jay Griffiths, writing in The Ecologist reported in October 2004: Metro: First line operation started in 2008. 2nd line operation started 2013. 2nd line expansion (L2B) started in 2014 and started operation on August 8, 2018. DAMM chosen to provide communication for GAIL pipeline in India. Damm.dk (2011-07-12). Retrieved on 2013-07-16.In the absence of a network, mobiles/portables can use 'direct mode' whereby they share channels directly (walkie-talkie mode). technical and power systems support communication, operations and dispatching, service agencies communication systems (police, Public health, firefighters, traffic control authority, road support). Aruba, Bonaire, Curaçao, Sint Maarten, Saint Martin, Saba, Sint Eustatius, and Anguilla operational