Actisense Smart NMEA Autoswitch

This is the first NMEA 0183 multiplexor I know of that can automatically switch to a back up input for any one of three reasons — “a failure to send any NMEA data, an invalid NMEA sentence checksum, or if the validity flag(s) contained within the NMEA sentence indicate that this data is not valid and should only be used with caution (for GPS and Depth data)”. In other words, you could have 4 GPSs (or, more likely 2 GPSs and 2 sounders) feeding the best available data to, say, a plotter and a PC…no manual backup switches needed. Very slick. Actisense’s site has lots of good information on the NSW-1, and it’s available for 260 pounds from at least one English online retailer (the U.S. distributor is Gem Electronics, 843–394–3565).