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UNIT 7 COMMUNICATION

UNIT 7 COMMUNICATION. DSC. Digital Selective Calling (DSC) is a calling system to call ships and coast stations using frequencies in the MF, HF or VHF bands. VHF-DSC. DSC calls can also be made to individual ships or groups of ships.

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UNIT 7 COMMUNICATION

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  1. UNIT 7COMMUNICATION DSC

  2. Digital Selective Calling (DSC) is a calling system to call ships and coast stations using frequencies in the MF, HF or VHF bands

  3. VHF-DSC

  4. DSC calls can also be made to individual ships or groups of ships.

  5. DSC distress alerts are used for initiating emergency communications with ships and rescue coordination centres

  6. The DSC-equipped VHF and MF/HF radios shall be connected to a satellite navigation receiver for ensuring accurate location information.

  7. The content of a DSC call includes the numerical address of the station to which the call transmitted.

  8. The types of DSC calls are • Distress • Urgency • Safety • Routine

  9. The ITU (International Telecommunication Union) has allocated a DSC distress and safety channel in the MF/ HF and the VHF marine radio bands. These are: • MF/HF DSC, 2187.5, 4207.5, 6312.0, 8414.5, 12577.0, 16804.5 (kHz) • VHF DSC, VHF marine channel 70.

  10. The MF/HF channels are restricted to distress, urgency and safety traffic only because of the relatively low speeds of transmission of 100 baud.

  11. If too many calls were permitted on the MF/HF channels, the channels would quickly become overloaded to the point where a distress call may be blocked. VHF DSC operates at 12 times the speed of MF/HF.

  12. Urgency, safety and routine calls can be addressed to all stations, an individual station, or a group of stations.

  13. All DSC equipment is programmed with a unique nine digit identification number, known as a Maritime Mobile Service Identity (MMSI). • The MMSI is sent automatically with each and every DSC transmission made.

  14. The first three digits of the MMSI are known as the Maritime Identification Digits (MID). • The MID represents the country of registration of the vessel, or the country in which the DSC shore station is located.

  15. The DSC modem decodes all calls on the frequency to which the receiver is tuned. If calls are received, the DSC controller sounds an alarm, and displays the decoded information on the alpha-numeric display.

  16. To transmit a DSC call, a GMDSS operator enters the required commands to identify the station (or stations), the priority (distress, urgent, safety or routine) and the purpose of the call. Once the call is composed, the CALL button is pressed on the DSC controller, and the information is sent to the associated transmitter for transmission

  17. 1- What is a distress alert used for?

  18. 2- Why shall the DSC-equipped VHF and MF/HF radios be connected to a satellite navigation receiver?

  19. 3- What are the types of DSC calls?

  20. 4- Who allocates the radio bands?

  21. 5-What does MID stand for?

  22. SOME WORDS Baud (n) - Data transmission rate for modems.

  23. Distress (n) - State of danger, trouble.

  24. Emergency (n) - A sudden unforeseen crisis that requires immediate action.

  25. Urgency (n) - State of being urgent, needing immediate attention.

  26. Rescue (v) - To save from harm, to deliver from danger.

  27. Rewrite each sentence using AND, BUT or OR. Make any changes if necessary. 1-a) INMARSAT is a satellite system./ It provides voice, data and distress communication. b) INMARSAT is a satellite system and provides voice, data and distress communication.

  28. 2-VHF has a short range. / HF has a long range.

  29. 3-Transit was the first satellite navigation system. GPS supplanted it as a result of growing technology.

  30. All DSC equipment is programmed with a unique nine digit identification number. It is known as MMSI.

  31. What statement is not true regarding DSC call? a. The content of a DSC call includes the numerical address of the station. b. DSC calls can also be made to individual ships or groups of ships c. DSC calls are used for initiating emergency communications. d. DSC call can be transmitted via MF/HF or VHF. e. The types of DSC calls do not include urgency calls.

  32. What statement is not true regarding DSC call? e. The types of DSC calls do not include urgency calls.

  33. I-Routine II-Distress III-Urgency IV-Security True order of the priority of calls is; a. I-III-IV-II b. II-III-IV-I c. II-IV-III-I d. II-I-III-IV e. III-IV-II-I

  34. I-Routine II-Distress III-Urgency IV-Security True order of the priority of calls is; b. II-III-IV-I

  35. How many VHF frequencies are available for DSC calls? a. 1 b. 2 c. 3 d. 7 e. none

  36. How many VHF frequencies are available for DSC calls? a. 1

  37. How many frequencies are available for DSC calls? a. 1 b. 4 c. 7 d. 5 e. 2

  38. How many frequencies are available for DSC calls? c. 7

  39. DSC is primarily used to; a. receive weather warnings, navigational notices and other marine safety information. b. provide routine communications with the ship owner. c. transmit and receive distress and safety alerts to and from other ships and shore stations via radio. d. report ship's position to search-and-rescue authorities via satellite. e. helps navigator to find the position

  40. DSC is primarily used to; c. transmit and receive distress and safety alerts to and from other ships and shore stations via radio.

  41. Which channel is designated for DSC? a. Channel 06 b. Channel 70 c. Channel 16 d. Channel 13 e. Channel 17

  42. Which channel is designated for DSC? b. Channel 70

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