Com port splitter create more port for each application to use. If you not using it, you ONLY have 1 com port with GPS data. With that 1 available port, you can either use it for iGuidance or RoadRunner or any other GSP app you have. RoadRunner use GPS data for Speed, Heading Direction (in Degree or N,S,E,W), altitude and many other. What cool about it is that there are many flash base GPS speedo that can be use for show
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