Raymarine Ray230 Owner's Handbook Manual page 52

Operations
4. Handset 1 is Off-Hook while other stations are On-Hook
Operation possible
5. Handset 1 is Off-Hook while another Handset is Off-Hook
Operation possible
6. All Handsets are Off-Hook
Operation possible
Handset Display
The dot matrix display indicates the handset's rank. If Handset 1 has
priority, for example, the message AVAILABLE is displayed on the LCD of
Handset 1 while HANDSET 1 (or the currently assigned handset name) is
displayed on the LCD of the other handsets.
Handset 1 Handset 2
OFF-Hook On-Hook
Operation disabled
Handset 1 Handset 2
OFF-Hook On-Hook
Operation disabled
Handset 1 Handset 2
OFF-Hook OFF-Hook
Operation limited
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Handset 3
On-Hook
Operation disabled
Handset 3
OFF-Hook
Operation limited
Handset 3
OFF-Hook
Operation disabled