Raymarine DSM250, Owner'S Handbook Manual

Page: 51 / 122

Chapter 4: System Setup 4-9
Manual Mode
If you select Manual mode, by pressing either of the
MANUAL
keys, you can specify the local variation value according to the
area in which you are operating.
Press the appropriate
MANUAL
key to adjust the variation up or
down, to a maximum of 30° East or West.
This value is then transmitted to any other SeaTalk instruments on
your system. It is retained if you turn the display off and on again.
In Manual mode, incoming NMEA variation is ignored. However,
if the variation is changed on another SeaTalk instrument, the new
value is used and the manual value that is displayed is updated.
Note: The Manual variation value defaults to 0°, so it is important to
set up a value if variation is not available from an external source.
Bridge NMEA Heading
The display unit sends NMEA input data to the SeaTalk bus. The
Bridge NMEA Heading option can be used to prevent NMEA
heading data being bridged onto the SeaTalk bus.
For example, if you have a course computer connected on SeaTalk
and NMEA, and an active compass connected on NMEA (for
MARPA), SeaTalk data overrides NMEA data in the course com-
puter.
You should therefore switch
OFF
the Bridge NMEA Heading
option to ensure the course computer receives the same NMEA
heading input as the rest of the system.
NMEA-Out Set Up
This option lets you disable the transmission of specific NMEA
sentences, which may be necessary if you have other instruments
sending the same data as your sounder.
For example, if the DPT (depth) sentence is set
ON
but the
sounder’s transducer is designed to sense temperature and speed
only, the depth value will be transmitted as zero. If you also have
an ST60 Depth instrument installed, there may be confusion
between the zero depth sent by the sounder and the actual depth
sent by the ST60. Turning
OFF
the DPT sentence disables the read-
ing from the sounder.