NMEA Buffer


Safely drive up to six NMEA Listeners,

with power distribution for the

connected Talker...



What are the NMEA 0183 Listener and Talker Designations?

The NMEA have updated the NMEA 0183 specification to ensure a consistent naming convention is used for labelling ports. The designation follows the same rules as used for Rx and Tx labelling but uses the descriptions’ Talker’ and ‘Listener’ instead. The input/receiving (Rx) port on a device will be labelled as a ‘Listener’ port. The output/transmitting (Tx) port on a device will be labelled as a ‘Talker’ port. When a port is labelled ‘Listener’ it is an input and when it is labelled ‘Talker’ it is an output.


Is the NBF-3 a direct replacement for the NBF-2?

The NBF-3 is a replacement for the NBF-2. The NBF-3 has the same functionality as the NBF-2 with the addition of a fused power output for powering the NMEA Talker device (that supplies the NBF-3 with data). The new case design allows for quicker and easier connections whilst keeping the electronics fully protected. The NBF-2 will be retired from production at the end of 2013.


Does the NBF-3 need external power?

Yes, the NBF-3 requires a supply between 10 to 35V DC and will use a maximum of 100mA at 12V DC (when all outputs are fully loaded with 100?). This does not include the current draw of the NBF-3 ‘Power Output’ that can be used to power an NMEA Talker device up to an additional 500mA.


What if my NMEA Listener does not have an isolated input or uses ground for the negative data connection?

The NMEA 0183 specification, from version 2 (1996) onwards, requires a device’s Listener port to be isolated. Some NMEA 0183 devices however choose instead to follow version 1 of the specification which allowed for non-isolated inputs to be used.

The NBF-3 Talker/Output ports are all isolated so that an NMEA Listener (or other device) without an isolated input can be safely connected with no fear of ground-loop damage. Isolation is between every NBF-3 connection; power, Listener/Input port and all Talker/Output ports.

Can I use the NBF-3 with data that is not NMEA 0183?

Yes, the NBF-3 will generate an identical copy of the electrical signal it receives on its input port to each of its output ports. The electrical signal must use RS422, RS485 or RS232 voltage levels for its ‘High’ and ‘Low’ data levels.

As the NBF-3 only ‘sees’ the electrical signals, the data protocol used is not relevant and no protocol validation of the data is performed. Each output will be an identical copy of the input data regardless of the data protocol. The output voltage levels are amplified to RS422/RS485 levels when a differential input device is connected and and to voltage levels compatible with RS232 when a single-ended device is connected.


What is the NBF-3 power output for?

When connecting an NMEA Talker device to the NBF-3 Listener port, it is possible to also power the NMEA Talker device from the NBF-3. This means only a single cable need be run between the NMEA Talker device and the NBF-3, reducing installation time and cost. The NBF-3 ‘Power Output’connection has a self-resettable fuse providing up to 500mA to the NMEA Talker device at the voltage supplied to the NBF-3. Please refer to the specifications in the user manual for more detail.


What NBF-3 variants are available and what do I get in the box?

There is only one variant of the NBF-3. If you are interested in a special OEM variant, please contact Actisense support.
1 x NBF-3 with pluggable screw terminals.
1 x Actisense CD in sleeve (Documents and Software)
1 x NBF-3 User Manual
1 x Connector cover
4 x Connector cover screws
4 x Mounting screws


What are the connections on the NBF-3?

The NBF-3 has nine connection pairs:
One power input pair for powering the NBF-3.
One power output pair for powering the NMEA Talker device.
One Listener / Input port pair to receive data from the NMEA Talker device.
Six Talker / Output port pairs to distribute data to the NMEA Listener devices.
Each connection pair is made with a pluggable screw terminal connector for easy installation.


Can I connect more than one NMEA Listener device to a single NBF-3 Talker port?

Yes, but there are several things to consider; firstly, each NBF-3 Talker port can drive up to 20mA. Check the sum of currents for all the NMEA Listener devices does not exceed 20mA. As a guide, the NMEA 0183 specification states that an NMEA 0183 Listener port should not draw more than 2mA, but some do require more.

Also, each Talker port is fully isolated; however the NBF-3 cannot provide isolation between the multiple Listener devices connected to a single Talker port. Connecting more than one NMEA Listener device is only recommended when all devices are known to have isolated inputs.

The total cable length and cable quality will also affect the number of devices that can be connected.


What are the NBF-3 mounting options?

A DIN Rail mounting kit is available to order from Actisense. The kit is not supplied with the NBF-3-BAS. The kit is suitable for use with top hat rail, type EN 50 022 or G section rail, type EN 50 035.

The kit can be ordered using part number: DIN-KIT-1.

The NBF-3 can also be mounted on the bulkhead. Four M4 stainless steel pan-head screws are provided with the NBF-3 for mounting to the bulkhead.


end faq

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