Raymarine Ray230 Owner's Handbook Manual page 58

Operations
Note: Only simplex channels (those channels that transmit and receive
on the same frequency) can be selected for ship to ship Individual Calls.
Pressing the SQ UP/DOWN will scroll you through the simplex channels
usable for this operation.
Response
If a response is received after pressing the PTT switch, a receive-
confirmation message is displayed. After 5 seconds have elapsed, the
channel is changed to a communication channel and the Individual Ships
Call is completed.
If no response is received for 3 minutes after pressing the PTT switch, a
prompt to press the PTT switch appears once more. After 15 seconds
elapses without pressing the PTT switch following the prompt, operation
returns to the state before the call.
PTT
ENT
MMSI number or
nickname is displayed
ACK
3 min
NO ACK
Scrolls every second
ENT
5 sec
PTT
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