Standard Horizon HX-870 - Manual (Page 53)

Page 53 HX870
10.6 GROUP CALL
This feature allows the user to contact a group of specific vessels (e.g. members
of a yacht club) using DSC radios with the group call function to automatically
switch to a desired channel for voice communications. This function is very
useful for yacht clubs and vessels traveling together that want to collectively
make announcements on a predetermined channel. Up to 20 group MMSIs
may be programmed.
10.6.1 Setting up a Group Call
For this function to operate, the same group MMSI (Maritime Mobile Service
Identity Number) must be programmed into all the DSC VHF radios within the
group of vessels that will be using this feature. To understand Group MMSI
programming, first a ship MMSI has to be understood.
Ship MMSI: The first three digits called MID (Mobile Identity Group) of a ship
MMSI denote the country where the ship’s MMSI is registered. The last 6 digits
are specific to the ships ID.
Ship MMSI Example: If your MMSI is “366123456”, “366” is MID which denote
the country and “123456” is your ships MMSI.
Group MMSI:
 Group MMSI numbers are not assigned by the FCC or other organizations
licensed to assign ship MMSI numbers.
 The first digit of a group MMSI is always set to “0” by International rules. All
Standard Horizon radios are preset so when programming a group MMSI
the first digit is set to “0”.
 The USCG recommends programming the MID of a ship MMSI into the
Second, Third and Fourth digits of the group MMSI as it denotes the area
the ship is located in.
 The last 5 digits are decided upon by persons in the group. This is an impor-
tant step as all radios in the group must contain the same group MMSI so
they can be contacted by each other. There is a chance that another group
of vessels may program in the same group MMSI. If this happens, simply
change one or more of the last 5 digits of the group MMSI.