The iMux

The Brookhouse WiFi NMEA 0183 multiplexer for the iPad, iPhone, iPod touch, Windows computers, Macs and Androids.  

Marine navigation using an iPad or other i-device or Android has come of age. Oceans have been crossed with  the Apple iPad as the primary navigation tool and many regattas have been sailed with the iPad playing a major role in the hands of the tactician. iNavx  for i-devices is in our opinion still the most powerful navigation app with rich features including plotting of AIS targets and full instruments support, but the list of  quality apps in this category is growing.  The offerings for Androids have been lagging behind, but there are now some promising apps available in the Google Play app store. The iPad with iNavX offers chart plotter features at a fraction of the cost. The iRegatta app is extremely useful for racing and the NMEA-Remote app offers large instrument displays that compete with dedicated instruments, in particular as repeater at  the vessel's navstation. 

The Brookhouse iMux is the most versatile and reliable product available today to feed multiplexed data from GPS, AIS and a multitude of instruments to  iPads, Androids, laptops etc. via wifi. The iMux Mk3, launched in August 2013 supports 16 simultaneous TCP connections in infrastructure mode as a NMEA server. Other features include WPA2 security and DHCP.  The Brookhouse iMux does not use the simpler UDP protocol, as some other products do for multiple connections. We feel that the risk of undetected data-loss of the UDP protocol makes it unsuitable for AIS data transmission. The iMux can be integrated with an existing wifi network, so that  a single access point (AP) can be used for all wifi traffic. Click here for details. Boat owners do not have to be network or electronics specialists to install the iMux. In most cases installation is "out of the box", without the need for configuration. For joining an existing network, a web-page is available for configuration. This web page can be accessed via any browser, e.g. Safari, Google Chrome or Internet explorer. 

The Brookhouse iMux and iMux-ST offer superior features, unequalled by any other Wifi enabled NMEA 0183 multiplexer available today. Please compare:

  • Data from multiple instruments, GPS, AIS, etc., is transmitted via Wifi. The iMux creates its own network and can be accessed as a wireless access point by up to 16 simultaneous users anywhere on the vessel or can be integrated with another on-board  network.

  • All users can receive and send data simultaneously using safe TCP connections, not the simpler UDP protocol which is unsafe and unsuitable for AIS transmissions.

  • An internal configuration web page is available for joining another wifi network. Click here for details.

  • WPA2 security with a unique password for each iMux and DHCP for automatic IP address assignment.

  • The superior buffering technique used in all Brookhouse multiplexers makes data-overflow and buffer-delays  practically non-existent, even if instruments with high frequency output are connected, such as a fast heading sensor.

  • The iMux-ST offers integration with Seatalk1 networks. This option can be disabled which adds and an extra NMEA port. This is advantageous if future migration to non_Seatalk instruments is considered. 

  • All inputs are opto-isolated as recommended by the NMEA.

  • NMEA standard and high-speed baudrates are supported. (38400 baud for AIS).

  • Automatic switching between primary and backup GPS.

  • Baudrate conversion and routing allows connection of an auto pilot and DSC radios which can receive GPS and navigation data feed from various sources. 

  • The unique Brookhouse NMEA  "on the fly editing" allows conversion from and to different NMEA versions. As an example, this makes it possible to use an older auto pilot with a modern chart plotter. Uploadable scripts are available from Brookhouse, mostly for free.

  • Advanced filtering capabilities, not only on NMEA sentence type, but also on  other criteria.

  • Conditional routing capabilities.

  • The right balance between ease of installation and flexibility for special configurations is offered. While in most situations installation "out of the box" is possible without set-up procedure, detailed configuration options are available if and when necessary. 

  • In addition to the multiple wireless connections, the  iMux can be hard-wired to a chart plotter or computer.

Two iMux models are available:

  1. The standard NMEA 0183 iMux

  2. The iMux-ST for Raymarine Seatalk installations.

The standard iMux combines AIS data from any AIS receiver or transponder with GPS and NMEA instrument data and transmits the combined data stream via WiFi to the iPad, Android or computer. The iMux also has a serial output port for hard-wired connection to a chart plotter and/or a computer. All of the functions of the Brookhouse multiplexer model AIS are included, so application of this model is not limited to WiFi only. 

The iMux-ST converts Seatalk GPS and instrument data to NMEA 0183 and combines this data with AIS and data from other NMEA 0183 sources. The single  data stream is transmitted via WiFi for input by the iPad. In addition, the iMux-ST offers most of the features of multiplexer model AISC, for integration of AIS and other NMEA talkers with Raymarine chart plotters. The Seatalk GPS position is output as NMEA at 4800 baud and can be used as input by DSC VHF or SSB radios. 

The iMux is easy to install, no configuration is necessary unless the advanced features need to be enabled.

The WiFi capability of the iMux is not limited to wireless communication with i-devices or Androids. The iMux is also perfect for reliable wireless transmission of NMEA data to a laptop or other on-board navigation computer with wireless Lan adapter. All navigation programs that receive NMEA 0183  via a serial port,  USB or bluetooth can also work with the iMux.

For more about wifi and the capabilities of the iMux, click the following link: Brookhouse WIFI

In contrast to the other Brookhouse multiplexers, these 2 new multiplexers are “all-in” models without optional extras. Although most of the advanced features of the other models are available, including filtering and NMEA conversion, the aim has been to provide easy to install solutions that require minimal preparation and offer maximum features.

iPad models and prerequisites

The iPad 3G has an internal GPS, the WiFi only model does not have a real GPS and uses cell towers for “location services”. Both iPad models are suitable for use with the Brookhouse iMux, because external GPS, AIS and instrument data is received via WiFi. The vessel’s own accurate on-board GPS or DGPS is used for determining the position, not the internal iPad 3G GPS. The iMux-ST also transmits data from a Raymarine Seatalk GPS and Seatalk instruments. This means the iPad can be used for navigation anywhere on the boat without compromising GPS accuracy due to a blocked view of the sky. The internal GPS of the iPad 3G is a good back-up, but it is not a requirement.

iNavx for the iPad/iphone/iPod-touch is the recommended app for navigation, but there are now various alternatives, The iMux works with all of them.

Functionality offered by the standard iMux

  1. Combines NMEA data from 3 standard 4800baud NMEA talkers plus AIS at 38400 baud to a single data stream which is transmitted via WiFi.

  2. The combined data stream is also available at a 38400 baud serial output port to feed a chart plotter and/or computer.

  3. Baudrate conversion allows feeding a DSC VHF or SSB radio with position data from a chart plotter at 4800 baud if the chart plotter has a single NMEA output port that follows the baudrate of the NMEA input.

  4. An auto-pilot can be controlled by the iPad or chart plotter in “track-mode” (GPS mode) via the same port. 

  5. Waypoints can be created in iNavX on the iPad and transferred via Wifi to a computer or chartplotter. 

Functionality offered by the iMux-ST

  1. Translates Seatalk instrument and GPS data to NMEA 0183 and transmits all data in a single WiFi data stream for use by the iPad (or a computer) at 38400 baud.

  2. Transmits AIS output of an AIS receiver or transponder connected to the iMux via NMEA, combined with the instrument/GPS data of (1) above.

  3. Apart from the Seatalk and AIS ports, 2 more NMEA input ports are available for connection of extra NMEA talkers, e.g. a fast heading sensor and DSC/DSE output of a DSC radio or a backup NMEA GPS.

  4. Besides WiFi output, the combined data stream is also available at a 38400 baud output port for connection to the NMEA IN port of a chart plotter, such as a Raymarine C/E series.

  5. Converted Seatalk GPS data is also made available on a 4800 baud NMEA out port and can be used as lat/long input for a VHF radio.

  6. Baudrate conversion of chart plotter NMEA output from 38400 to 4800 is available. Since the multiplexer outputs GPS data, obtained directly from Seatalk, chart plotter NMEA output will only be required in special cases and the plotter’s NMEA output usually does not need to be connected. 

  7. Waypoint transfer from iNavX to the iPad. 

    All of the above functionality is available with factory settings.

How we see the role of the iPad on boats with Seatalk instruments.

Many production boats are delivered with a standard Raymarine instrument pack (speed/log, depth, wind) and a Raymarine chart plotter with GPS at the helm as an optional extra.
The iPad, paired with a Brookhouse iMux can be a low-cost alternative for a chart plotter. Naturally,  the iPad does not offer the same level of ruggedness as a purpose-built chart plotter. However, much can be done to protect the iPad against the elements and other risks of damage on board a boat. Waterproof covers and mounting brackets are widely available.

While the iPad’s function as the main chart plotter on a sea-going vessel is debatable, its powerful features can also be a tremendous complement to a fixed chart plotter at the helm: 

  • When sailing under difficult circumstances, when the helmsman has to concentrate on steering the boat, another crew member can be given the task of checking AIS targets and other navigational data on an iPad in any convenient position.

  • An iPad, semi-permanently fixed at the chart table makes a great repeater for Seatalk instruments.

  • Because the iPad receives GPS, AIS and instrument data independently from the iMux, it is an excellent backup for the C- or E-series or any other model chart plotter.

  • If the boat has an older generation chart plotter without AIS support, such as the Raymarine Pathfinder series, instead of buying a new chart plotter with AIS, an iPad with Brookhouse iMux will offer the additional functionality.

  • Since the iPad has powerful email and net-browsing capabilities, in many cases it can be used instead of an onboard computer. To improve the 3G range, a small 3G router installed in an elevated position can be considered. 

General specifications
standard iMux

  • · 4 opto-isolated “NMEA Listener” (Input) ports, 3 at 4800 bps, 1 at 38400 bps for AIS.

  • 1  RS232 output port  for connection to a chart plotter or computer

  • 1 RS232 input port 
    (baudrate conversion input).

  • 1 Output RS422 port (differential NMEA talker port) 4800bps
    (baudrate conversion output)

  • Baudrate conversion 38400bps-4800bps.

  • Indicators: red LED for power, green LED for data-transmission.

  • Supply Voltage: DC 9-35 Volts.

  • Reversed polarity protection.

  • Physical size: 110x65x37mm (hxwxd)

  • Weight: 140 grams

  • Mounting: bulkhead mounting with screws.

  • NMEA management and control:

    • NMEA Sentence Filtering

    • NMEA Sentence editing “on the fly” for NMEA protocol conversion.

    • Automatic port switching.

General specifications

Specifications are the same as for the standard model with 2 exceptions:

  • Instead of 3 NMEA 4800 input ports the iMux-ST has 1 Seatalk port and 2 NMEA 4800 baud input ports. If the Seatalk port is disabled, a 3rd NMEA input @ 4800 is available.

  • Seatalk GPS data, if available, is always sent to the 4800 output port as input for a DSC radio.

    *All popular AIS receivers and transponders are supported.

WiFi specs

  • Up to 16 TCP/IP sessions

  • DHCP

  • WPA2 security

  •  2.4 GHz 802.11 b/g transceiver

  •  low power

  •  internal chip antenna

  •  FCC/CE/ ICS certified

The iMux WiFi range has been tested on several types of boats. Installed in a cabinet or behind an instrument panel, a range of 10 meters is not a problem for the internal chip antenna. For most installations this is adequate. This is only an indication, circumstances differ from boat to boat. In some cases it may be necessary to experiment with the location to achieve the best performance.

An optional external antenna connection is available if required. 

More reading about multiplexers:

Please click this link: What to look for:



Pricing, ordering and payment 



Note: Seatalk is a trade-mark of RayMarine.




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