Editing Digital selective calling (section)

==Workings==
DSC was developed to replace a voice call in older procedures. Because a DSC signal uses a stable signal with a narrow bandwidth and the receiver has no [[squelch]], it has a slightly longer range than [[analog signal]]s,<ref name=b35 /> with up to twenty-five percent longer range and significantly faster.<ref>Payne (2006): 4</ref> DSC senders are programmed with the ship's [[Maritime Mobile Service Identity]] (MMSI) and may be connected to the ship's [[Global Positioning System]] (GPS), which allows the apparatus to know who it is, what time it is and where it is. This allows a [[distress signal]] to be sent very quickly.<ref name=b35 />

Often, ships use separate VHF DSC and MF/HF DSC controllers. For VHF, DSC has its own dedicated [[Receiver (radio)|receiver]] for monitoring Channel 70, but uses the main VHF transceiver for [[transmission (telecommunications)|transmission]]. However, for the user, the controller is often a single unit.<ref name=b35 /> MF/HF DSC devices monitor multiple bands for distress, [[pan-pan|urgency]] and safety ''[[sécurité]]'' transmissions in the 2, 4, 6, 8, 12 and 16&nbsp;[[Hertz|MHz]] marine bands. At minimum, controllers will monitor 2187.5&nbsp;kHz and 8414.5&nbsp;kHz and one more band.<ref name=b37>Bréhaut (2009): 37</ref> However for automated monitoring a second, receive-only antenna is often needed (especially on non-commercial leisure boats) since a separate tuner is used apart from the main one;<ref name="metzcomm">{{cite web | url = http://www.metzcommunication.com/weatherf.htm | title = General Coverage / WeatherFAX / DSC Antenna | accessdate = 2016-05-17 | publisher = Metz Communication }}</ref><ref name="imc802an2">{{cite web | url = http://www.cruisersforum.com/forums/f13/icom-m802-dsc-antenna-10542.html | title = ICOM M802 DSC antenna? | date = 2007-10-15 | work = Cruiser's Forum }}</ref> this is separate from programming radios to monitor user-defined DSC frequencies (which would use the main antenna).<ref name="hfdsc2015">{{cite web | url = http://yachtzenagain.blogspot.com/2015/06/hfssb-dsc-routine-calling-with-icom.html | title = HF/SSB DSC Routine Calling with Icom M801E/M802 | work = Yacht Zen Again Weblog | date = 2015-06-10 | first =  Mike | last = Reynolds}}</ref><ref name="hfdsc2016">{{cite web | url = http://yachtzenagain.blogspot.com/2016/04/dsc-global-navarea-group-ids.html | title =  DSC Global NavArea Group IDs | work = Yacht Zen Again Weblog | date = 2016-04-17 | first =  Mike | last = Reynolds}}</ref>