Nmea0183 Port Connections
HOW TO CONNECT A NMEA0183 TALKER TO A NMEAXWIFI MULTIPLEXER
The connections of output devices (also referred to as Nmea 0183 talkers) to the Vela-Navega multiplexers are shown in the following picture. If your Nmea data is available though a Differential Output device, the preferred way is to connect its A (or Nmea+) terminal to the multiplexer A and its B (or Nmea-) terminal to the multiplexer B. You could also connect GND to B. If your Nmea data is available through a Single Ended Output device (such as RS-232) you connect its Output terminal to the multiplexer A and its Ground (or common) terminal to the multiplexer B.
HOW TO CONNECT A NMEAXWIFI MULTIPLEXER TO A NMEA0183 LISTENER
We now consider the connection of the output serial port which uses a 3-pin (screw or spring) connector with labels A B and GND (old units) or a 2-pin (screw or spring) with labels A and B plus a jumper with positions 1 and 2 (recent units). If the receiving device has an opto-isolated port, you connect A to the A (or Nmea+) terminal of the receiving device and B to the B (or Nmea-) terminal of the receiving device. You could also connect GND to B (or Nmea-). If the input port of the receiving device is not opto-isolated you should take special attention to the connections. You should connect A to the input terminal of the receiving device and not use B. In addition, both GNDs (multiplexer and receiving device) should be connected together.
If you connect B to the GND of the receiving device, you may destroy the output driver of the multiplexer. In order to avoid this possibility, the output port of recent multiplexers have only a 2-pin connector with labels A and B instead of A, B and GND. However the B pin can be configured through a jumper. In position 1 (default) B is connected to GND making the output port of the multiplexer a Single Ended Output. In position 2, B is connected to the negative driver output, making the output port of the multiplexer a Differential Output.
Note that the P2 output port of the N2K0183 multiplexer only has 2 pins (A2 and B2) and no jumper. You should only connect the P2 output of the N2K0183 to an opto isolated listener or follow the instructions to "transform" a single ended input device into an opto isolated device using the adapters described here.