Subelement L: L – Installation, Maintenance & Repair— Topic 81: Troubleshooting
Question 3-81L6
Element 3 (GROL)What steps must be taken to activate the DSC emergency signaling function on a marine VHF?
Explanation
Digital Selective Calling (DSC) functions, particularly for emergency signaling, rely on a unique identifier for your vessel. The 9-digit Mobile Maritime Service Identity (MMSI) serves as this unique electronic "address" for your vessel within the global maritime communications system. When a DSC distress alert is sent, it *must* include the vessel's MMSI so that rescue authorities and other vessels can identify the source of the distress and respond appropriately. Without a programmed MMSI, the radio cannot generate a valid DSC message, thus preventing the activation of its emergency signaling capabilities.
While GPS position input (C) is extremely important for a *useful* DSC distress alert, allowing rescuers to locate you, the radio's fundamental ability to transmit a DSC message and identify itself first requires the MMSI. Options A and B are incorrect; a marine VHF requires a single 12-volt power source and generally uses one antenna for both voice and DSC.
Related Questions
3-81L4 In a software-defined transceiver, what would be the best way for a technician to make a quick overall evaluation of the radio’s operational condition?3-81L5 How might an installer verify correct GPS sentence to marine DSC VHF radio?3-82M1 What term describes a wide-bandwidth communications system in which the RF carrier frequency varies according to some predetermined sequence?3-82M2 Name two types of spread spectrum systems used in most RF communications applications?3-82M3 What is the term used to describe a spread spectrum communications system where the center frequency of a conventional carrier is altered many times per second in accordance with a pseudo-random list of channels?