Most equipment on a boat is connected to at least one other piece of equipment. For example the GPS unit is connected to the DSC VHF radio, the AIS receiver is connected to the ChartPlotter. This inter-connection is called a “Network”.
NMEA0183 – Each network may have only one talker (data sender) but many listeners (data receiver). The standard is intended to support one-way serial data transmission from a single talker to one or more listeners. This data may include information such as position, speed, depth, frequency allocation, etc.
There are two different speeds used:-
4800Bd = “Normal Speed” used for position, speed, depth etc
38400Bd = “High Speed” used for AIS data.
The two are NOT interchangeable and whilst position, speed and depth data can also be sent at 38400Bd, AIS cannot be sent at 4800Bd.
Interconnecting equipment is thus simply a case of joining the equipment together with a multi-core cable (usually 3-core) ensuring the colours of the wires are correct (different manufacturers use different colours for OUT+/TX+/B etc.
You should note that most Garmin Chartplotters use a slightly different interface to everyone else and some equipment (e.g. Quark AIS Receivers) may need and Interface Board to operate correctly.
The Interface Board is primarily designed for Garmin devices running the NMEA 0183 with a single ended output. It can be very hard to determine whether your Garmin device is using this single ended signal. The best way to find out what signal is being sent out is to read the manual carefully looking for references to NMEA or to call Garmin themselves or us. We often see TX and RX for devices needing the Garmin bridge. This is the single output compared with the differential NMEA OUT-/A and NMEA OUT+/B.
Generally speaking Garmin devices especially chart plotters on or below the 3000 series are outputting in a single ended capacity. Newer devices like the Garmin 4000 typically use a differential output. The advice is to always ask before buying or to ring the manufacturer up to ask and check.
There is also a Raymarine version of NMEA0183 called “SeaTalk” or “SeaTalk1”. This is slightly different to a standard NMEA0183 network in that any number of “Talkers” can be added to the network. An external interface is required to connect SeaTalk equipment to other manufacturer’s equipment.
It is not normally possible to connect more than one “Talker” to a network, nor is it possible to connect a 4800Bd device to a 38400Bd device. However, this can be done with a device known as a Multiplexer. There are several different ones available depending on your requirement. See others.
NMEA2000 – Each network is a moderate capacity bi-directional, multi-transmitter/multi-receiver instrument network to interconnect marine electronic devices. It is multi-master and self configuring, and there is no central network controller. Equipment designed to this standard will have the ability to share data, including commands and status with other compatible equipment over a single channel. It is based on CAN (Controller Area Network). All NMEA 2000® products must be certified by NMEA. Although this standard is 50 times faster than NMEA 0183, it is not intended to support high-bandwidth applications such as video.
Before connecting any equipment, you first need a basic NMEA2000 network to be installed in your boat if there isn’t already one there. Once the network is installed, it is then simply a case of connecting each piece of equipment to a “Tee” connector in the network via a “Spur” cable.
Typical “NMEA2000 Starter Kits” are from Garmin and Actisense.
It is possiblt to interconnect NMEA0183 and NMEA2000 networks by using a “Data Gateway” or Converter. But you must use the correct one; for example to connect an NMEA0183 Hi-Speed network, use the Actisense AIS product.
In theory therefore, any piece of equipment from any manufacturer can simply be connected to the network. However, Raymarine (plus a couple of other, smaller manufacturers) have their own version of the connectors used so you must use an interface cable to interconnect Raymaine “SeaTalkNG” or “DeviceNet” equipment to any other manufacturer’s equipment.