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178 | Simrad MX500

NMEA Interface

The MX500 meets the NMEA 0183 version 2.3 electrical

standard for marine interface communications with other

marine equipment, such as:

Radars, Plotters, Autopilots, Fish Finders, etc.

There are differences in the electrical interface speci-

fication between NMEA 0183 version 1.5 (introduced in

1987) and NMEA 0183 version 2.0 and later (introduced

in 1994). Some older model equipment utilize RS-232,

others use RS-422, and others meet the older version

1.5 specification. In an effort to simplify your interface

capabilities, you should take the time to determine which

electrical interface specification all of the interfaced

equipment meets.

NMEA Interface to other Equipment

The MX500 meets NMEA 0183 version 2.3 electrically,

and in protocol. As version 2.1 is not necessarily compat-

ible with the older version 1.5, the differences in hard-

ware are mentioned here to avoid possible conflicts:

Listener:

The listener input works with a threshold of 2 volts com-

pared to the former 4 volt. It is still an insulated input

and, in general, there should not be any interface prob-

lems receiving data from the older standard.

Talker:

The talker output is a RS-422 output:

NMEA talker output B is active compared to GND or

shield of the navigator. In the old version, output B was

normally tied to GND or shield.

The maximum drive voltage between the talker A and B

outputs is ±6 volt.

Compared to the former 0 to 15 volt output, the nega-

tive voltage between the talker A and B output may be

a problem on older listeners which do not meet the new

standard.

The minimum output voltage may be as low as ±2 volt.

This is not compatible with the former 4 volt input

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Memorex RX 1 Smart Installationshandbuch Seite 179