fire, you could not man the radio and fight the fire at the same time. DSC calling also helps cut back the transmission traffic on Ch. 16, the emergency priority channel.
How DSC works
A digital selective call uses a digital signal to transmit a pack of infor- mation that can include, the caller’s MMSI number, the MMSI of the ship or ships being called, call priority and a frequency or mode re- quest. Location and time of location may be entered manually or if an active GPS unit is attached, transmitted automatically. DSC calls allow you to contact a specific ship, a group of ships, a specific group of DSC receivers, ships in a particular geographic area or all ships within range of you. A DSC call may even be patched into a regular phone line through a commercial coastal station. One of the key elements of a DSC call is the ability to place an individual call directly to another vessel.
Simplex or Duplex
References to simplex and duplex channels are scattered throughout this manual. Simplex channels transmit and receive messages on the same frequency. Like a CB radio, only one message can be transmitted at a time. A duplex channel transmits and receives messages on differ- ent frequencies. Like a telephone, it gives users the capability to transmit and receive messages at the same time. You must choose a simplex channel when making a DSC call!
MMSI (Maritime Mobile Service Identity)
Your Maritime Mobile Service Identity number (MMSI) is like a home phone number. Other DSC (Digital Selective Calling) radios must enter your number before they can contact you. But first, you must program your number into your radio. If your MMSI number is not set up, the ID ANNUNCIATOR will blink on the display.
CAUTION
You only have one chance to program your MMSI into your ra- dio. Study this section carefully to ensure the MMSI is entered correctly.
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