The NMEA-Standard (National Marine Electronics Association) is a standard for transmissions in maritime area which exisits in different versions. It is mainly used by a worldwide navigation satellite system for passing-on position data for other devices (also: GNSS)
The NMEAMUX4 multiplexers can handle up to four incoming NMEA data streams which are multiplexed to up to 3 NMEA outputs streams. The modules are configurable through a windows configuration utility.
Because all inputs are routed 1:1 to all outputs (in the default configuration), this can lead into a buffer overflow. To avoid this, every NMEAMUX4/USB has a nonvolatile programmable black- and whitelist and routing matrix. With this list for every output can be configured which type of input messages should be routed to the specified output. As you know from microsoft products every prohibiton (blacklist) has a higher priority than an allowance ( whitelist ). With the routing matrix can be definied which inputs should be routed to a specific output.