Product Info

Y1-03-0174 Rev. A Draft
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SECTION 7 - GPSI/O Frequently Asked Question
Q. How do I download position data from my GPS to my beacon?
A. You must have a NMEA 0183 version 1.5 or higher output ready GPS unit and a GPS interface cable.
The NMEA 0183 optical interface connector supplied with your TerraFix must be connected to the
GPS interface cable using a universal serial adapter. Turn on your GPS unit and allow it to acquire
the necessary satellites. Make sure the output is set to NMEA 0183 with the GGA sentence
configured if necessary. Connect the NMEA 0183 interface cable to the GPS unit and the TerraFix.
The TerraFix will initiate a data preload when the GPS I/O button is pressed for more than ½ second
and less than 5 seconds.
Q. How long does it take to down load position coordinates from my GPS to my beacon?
A. Upon connection with a properly operating and fully acquired GPS unit, the ACR beacon usually
take less than four minutes to synchronize and download coordinates. Subsequent position updates
will take from a few seconds to no more than 20 seconds to complete.
Q. How does the GPS data get from my GPS to the beacon?
A. The GPS unit transmits data as electrical energy through the GPS interface cable to the ACR optical
interfacing connector. The ACR optical interfacing connector has an infrared LED and sensor located
in it. The electrical energy supplied by the GPS unit is converted to infrared light in the ACR optical
interfacing plug. Data from the GPS unit is transmitted via infrared light to the beacon through the
translucent beacon top cap or lens when the ACR optical interface plug is properly engaged. The
beacon has an infrared detector that decodes the light pulses. ACR uses an optical interface design to
eliminate the potential for leaks and corrosion common to mechanically interfacing devices. An external
LED flashes to confirm that GPS data is being sent from the handheld GPS.
Q. Does my beacon need any special set up to accept GPS data?
A. No. If it is hooked to a valid data source, that has been properly set up to deliver NMEA format with the
GPGGA sentence, it will automatically attempt to download the data and form an emergency message
that includes the position data when the preload function is initiated.
Q. Does my GPS unit have to be set up in a special way to transmit position coordinates via the
NMEA 0183 interface?
A. For the GPS to transmit data, go to GPS setup and make sure the NMEA 0183 output is turned on and
the GGA NMEA sentence is selected or turned on. Consult your GPS user’s manual for information on
configuring the NMEA output.
Q. What is the maximum length my GPS cable can be?
A. ACR Electronics recommends a maximum length of 400 feet using 24 AWG wire. Contact your GPS
owner’s manual for more detailed information.