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The NM-251D-DRU is a member of the NM-251 Series family and is programmed to function as a $xxDRU (Dual Doppler Auxiliary data) to $SDDPT or $SDDBT for delivering depth data information from older systems.
The NM-251D-DRU acquires the NMEA-0183 strings from the Ina port provided that they follow the 4.800/8/n/1 serial format. The NM-251D-DRU detects the $xxDRU string and converts it to $SDDPT or $SDDBT depending on the selected configuration in the dip switch array SW1.
The NM-251D-DRU can also be configured to replace the identifier of the speed log output string to VM or VW that is acceptable from modern ECDIS and VDR systems (converts $xxVBW to $VMVBW or $VWVBW). The NM-251D-DRU can also filter out all input stings except for depth and log data if this is selected from the dip switches.
Input Ports (listeners)
The NM-251D-DRU uses one of the two input ports. The input port Inb is not available at the NM-251D-DRU custom interface and should not be connected. The listener port Ina is optically isolated as specified in NMEA-0183 protocol, thus data(-) pole should never been connected to NM-251D-DRU ground. If the instrument’s talker port is single ended, connect that terminal to the Ina(+) input and tide the Ina(-) to instrument’s ground. If an RS-232 level signal is connected, the ground pole (GND) should be connected to Ina(+) and the data pole (TXD) to Ina(-) respectively.
The listener port Ina can acquire NMEA sentences carried in TTL, RS-232 and RS-485/422 signal levels.
Output Ports (Talkers)
Each of the four general purpose talker ports can output NMEA sentences in both RS422 and TTL signal levels, depending on the connection topology chosen (see figure 1, 2 and 3), and can fan out one instrument. Current drawn from all port can be up to 40mA (maximum rating 60mA @ 24VDC power supply) simultaneously, efficient enough to drive any NMEA compatible instrument.
Installation and Operation manual
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