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PC Active (NMEA/RS232) Interface Cable

If your system has a standard NMEA interface cable (9 pin D type connector and flying leads), then in all probability it will work well. However in noisy electrical environments or with long cable runs problems might be encountered. A solution is to use an active opto-isolated cable, this also reduces the risk of damage to your laptop during electrical storms (but can never fully protect)

Most personal computers communicate with the outside world via a protocol called RS232. NMEA and RS232 operate on slightly differing signal voltage levels and with some older equipment there is a danger of unreliable communication and possible damage to the computer serial port unless a suitable interface cable is used. Some GPS manufacturers supply suitable cables with their devices – if you have one of these, do check that it is fully opto-isolated and that it protects against reverse polarity before using it.

The active interface cable allows bi-directional transfer between NMEA and RS232 protocols, typically allowing data to come in to the PC from a GPS receiver or other instrument system, and simultaneously be transmitted to another device, such as an autopilot. As well as converting voltage levels between NMEA and RS232 levels, and protecting against reversed polarity, the listener (input) side is opto-isolated as per the NMEA specification. The electronics may be powered from the PC’s serial port, or from the boat’s 12V DC power supply (if your PC is unable to provide sufficient power or the software doesnt support setting the pins).

The electronics are housed in a 9-pin "D" connector, ready to connect to the serial port of most PCs; the 1m shielded cable has wires at the other end to connect to your NMEA device(s) and to a 12V power supply (if required).

Note: You will still need the appropriate cable to connect to the NMEA cable to your GPS,as this is specific to each GPS model.

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NMEA Listener/Input Isolation 2kV Opto-Isolation between Red/Black NMEA pair and all other connections

NMEA Listener/Input Voltage

+/-15V Continuous Maximum
+/-35V Max <1 Second

NMEA Listener/Input Signal Thresholds

Logic '0' +2V to +15V
Logic '1' -15V to 0V

NMEA Talker/Output Voltage & Current

Dependant on Host RS232 Interface. Typically +/-5V to +/-15V @10mA Max

RS232 Voltage on Host +/-7V to +/-15V
RS232 Port Total Current  Consumption 2mA to 5mA depending on RS232 Voltage
Speed/Baud Rate 4800 to 115200 Baud
Housing Material PVC Black
Thumb Screw Material PVC Orange
Screw Steel, Nickle Plated, M2.8 Thread
DB9 Connector 9 Pin Female
Cable Length ~1.5m
Cable Wire 22AWG (17/34AWG) Tinned Stranded Copper
Cable Jacket PVC
Shield Internal Copper Foil Shield
Cable Outer Diameter 5.5mm
Approvals and Certifications
Operating Temperature -20°C to +70°C
Electrical Specification Meets IEC 61162-2
Weight 100g
UL Certification Cable E137250
RoHs Compliant