Installation manual

Verbal Communication
Verbal communication is of two types: simplex and duplex.
• Simplex communication uses a single frequency, so only one transmitter can
be operating at any time. This means that each party in the conversation must
say ‘over’ when stopping transmitting so that the other party knows it is their
turn to transmit. All ship-to-ship communication is in simplex mode. The F1
DSC radiotelephone supports simplex communication.
• Duplex communication uses two frequencies, so both parties can talk at the
same time. The F1 DSC radiotelephone does not support full duplex operation.
• There is also a hybrid mode: semi-duplex. In this mode, one of the
communicating parties operates in duplex mode and the other in simplex. A
good example is ship to coast station communications. The F1 DSC
radiotelephone supports semi-duplex communication.
DSC Digital Communication
DSC (Digital Selective Calling) is a system for establishing communication to a
specified address, to a ‘group’ (a pre-defined set of addresses), or to ‘all parties’ for
a digital distress call.
The key feature of the DSC system is the use of the vessel’s MMSI (Maritime
Mobile Station Identity) number to identify each vessel. (This number is treated as
the vessel’s DSC telephone number.) Consequently, before a DSC call can be
made, the originating vessel’s MMSI must be programmed into its radio and the
receiving vessel’s MMSI must be known to the caller.
All DSC communication is on Channel 70. The radio maintains a continuous watch
on this channel for incoming messages, which are immediately reported. This
monitoring also allows the system to transmit only when the channel is free.
The radio responds to three types of DSC message:
All ships calls. These calls are received by all vessels within range of the
transmitter.
Individual calls. These calls are addressed specifically to the radio MMSI
number.
Group calls. When the radio has been set up as a member of a group, it
responds to calls addressed to the group number.