GMDSS英语阅读练习题(一)Digital Selective Calling SystemIntroductionDigital Selective Calling(DSC)is an integral part of the GMDSS and is used for transmittingdistress alerts from ships and for transmitting the associated acknowledgements from coaststations.The DSC system is very comprehensive and caters for the setting up of all types of callsusing internationally agreed codes.It is also used by ships and coast stations for relaying distressalerts and for other urgency and safety calls.DSC encoders/decoders,in some circumstances,canbe interfaced with existing equipment.A dedicated DSC watch receiver is required to keepcontinuous watch on the distress frequency,this can be a simple single channel receiver.Basic Description of DSCDSC is basically a calling system.Each call consists of a packet of digitised information ofone of four priorities:Distress,Urgency,Safety or Routine.Messages can be routed to”AllStations,to an individual station or to a group of stations,using their Maritime MobileSelective-call identity code(MMSI).Distress messages are automatically broadcast to AllSlations.In addition to the MMSI of source and destination stations,information can be conveyed inthe DSC message.For example,to aid the Rescue Services,the DSC Distress alert message isconfigured to contain the following:Ships identity(the nine digit MMSI);Time;Nature of distress(in the form of a standard code);Ships position.Where fitted,ships officers should ensure they are fully conversant with the procedure forentering the necessary information into the DSC equipment.At sea,unless provided automaticallyfrom a navigation system,ships position should be updated at least once during each watchperiod.Question:1、Each DSC”PACKET”have priority(priorities)A 1 B、2 C、3 D、42、Which of the following staement is not true&nbds?A、DSC message has a MMSI of source stationB、DSC message has a MMSI of source stationC、DSC message has a name of source stationD、A DSC message also has other information for sending round.3、Which of the following statement is true?A.Not every ship is required to keep continuous watch on the distressfrequency.B.A ship can keep a watch on the distress frequency at the time itthinks convenient.C.An exclusive DSC watch receiver is required to keep continuouswatch on the distress frequencies.D.A simple single channel receiver is not suitable for keeping continuouswatch on the distress frequency.4、at sea,if dsc equipment can not get shi is position message from anavigation system automatically,then the position message should berenewedA、at least every 4 hoursB、at least every 8 hoursC、at least every 12 hoursD、at least every 24 hours5、according to the message,distress message can be received by()A、ALL STATIONB、COAST SATIONC、SHIP STATIOND、GROUP OF SPECIFIED STATION(二)NAVTEX systemThe NAVTEX receiver is a Narrow Band Direct Printing(NBDP)device operating on thefrequency 518Khz,(some equipment can also operate on 490Khz and 4209.5Khz),and is a vitalpart of the Global Maritime Distress and Safety System(GMDSS).It is automatically receives Maritime Safety Information such as Radio NavigationalWarnings,Storm/Gale Warnings,Meteorological Forecasts,Piracy Warnings,Distress Alert etc.The information received is printed on the receivers own paper recorder roll.Each messagebegins with starts of message function(ZCZC)followed by a space then four B characters.TheFirst,(Bl),identifies the station being received,the second,(B2),identifies the subject i.e.Navigational Warning,Met Forecast etc,and the third and fourth,(B3+B4),form the consecutivenumber of the message from that station.This followed by the text of the message and ends withan end of message function(NNNN).The NAVTEX system broadcasts COASTAL WARNING which cover the area from thefairway buoy out to 250 nautical miles from the transmitter,the transmission from sometransmitters can be received out to 400 nautical miles and even further in unusual propagationconditions.Question:1.Which frequency is the NAVTEX receiver usually operatingon?A.490Khz B.4209.5Khz C.518Khz D.2182 Khz.2.Each message begins with starts of message function()?A.NNNNB.KKKKC.ZCZCD.NCNC3、Which of the following is no TRUE?A、Each message begin with starts of message function(ZCZC)B、Each message ends with an end of message function(nnnn)C、THE NAVTEX system can cover the 250miles from the transmitterD、THE NAVTEX system can not cover 400 miles from the transmitter(三)Terrestrial CommunicationsLong-Range ServiceUse of HF provides a long-rang service in both the ship-to-shore and shore-to-ship directions.In case covered by INMARSAT it can be used as an alternative to satellite communications andoutside these areas it provides the only long-rang communication capability.Frequencies havebeen designated in the 4,6,8,12 and 16 MHz bands for this service.Digital selective calling(DSC)forms the basis of distress alerting and safety communications.Distress and safety communications following a DSC call can be performed by radiotelephone orN