Simrad RS20S User Manual page 23

Contacts
Used for the administation and calling of all individual Contacts as
well as Groups.
View/Add Contact
Use this to store the names and associated MMSI's of up to 50
vessels to be called regularly using DSC. Contacts are stored by
name, in alphabetical order.
Select ADD NEW to create a new contact.
Selecting an existing name in the Contacts list gives the options to
place a DSC call, make a position request, edit the contact, or delete
the contact.
View/Add Group
Use this to create, edit, or delete up to 20 vessel groups, which are
stored in alphanumeric order. Only a name and a Group Call ID
(GCID) are required to set up a group. A GCID always starts with 0;
the remaining digits can be set to whatever the user desires. All
vessels intended to be in the same group must have a suitable DSC
radio, and have the identical GCID number entered.
Selecting an existing name in the group list gives the option to edit,
delete, or call the group.
¼ Note:
Adding a group to this list will in turn make the radio respond
to a group call made from any other radio with the same group
number in it's memory.
DSC call menu | RS20S User Guide