Garmin GPS 12 MAP Owner's Manual page 90

Setup Menu:
Interface
Select the 'RTCM/
NMEA' option to use the
GPS 12 MAP along with
a GARMIN Differential
Beacon Receiver.
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To select an input/output format:
1. Highlight the 'Format' field and press ENTER.
2. Select the desired setting and press ENTER.
3. If the 'GARMIN' format is selected, highlight the
'Transfer Mode' field and press ENTER. Select
the desired setting and press ENTER. The
'Transfer Mode' field allows you to specify what
information to request or send to a second GPS
12 MAP. The 'Host' setting lets you control all
data transfer functions from the second GPS 12
MAP or from a PC.
4. If an 'RTCM' format is selected, additional fields
are provided to control a GARMIN differential
beacon receiver (e.g. GBR 21) directly from your
GPS 12 MAP. You can enter the beacon
frequency and bit rate on the GPS 12 MAP and
the information will be used to tune the beacon
receiver. For more information, refer to the
owner's manual for your GARMIN differential
beacon receiver.