The National Marine Electronics Association is a group that governs a set of standards for intuitive and easier marine device networking. Incorporating laptops into systems like these create central control hubs for these devices. However, even older NMEA 0183 fishfinder devices can be connected directly to a laptop, creating a high-resolution screen for the device and offering extensive control options. Although some older fishfinders lack the ability to connect to a laptop or network, modern networked units are selected based on whether they will be installed in an NMEA 0183 or NMEA 2000 environment.
1NMEA 2000 Networks: Laptops and fishfinders connect to networks within the NMEA standard, offering bi-directional communication between the devices. NMEA 2000 devices are connected into a central network, with units such as laptops, fishfinders, GPS and diagnostic electronics forming the core of a fully equipped vessel. The network does not require a central controller, using instead what is called a controller area network, or CAN. Commonly used in vehicles of all types including marine vessels, CAN bus systems allow devices to communicate to each other without the individual signals requiring processing through a central controller module. Within these environments, older NMEA 0183 devices may still be integrated using appropriate adapters. Although data and graphics flow freely through these networks, they lack the capacity for full-motion video.
2NMEA 0183 Direct Connection: Many vessels still incorporate NMEA 0183 devices, primarily due to familiarity and ease of use. Many NMEA 0183 fishfinders connect to laptops directly using USB or 4,800-baud serial connections. The advantage of devices like these is that the central processing unit's cost is dramatically reduced since they lack built-in monitors, using the laptop's screen as the display. Additionally, more software, data processing and storage is enabled, using the power of the connected computer. Units such as these are kept current via standard firmware updates, downloaded and installed through the laptop
3Connectors and Cabling: Each NMEA 2000 DeviceNet network is assembled using an 8-amp central backbone cable. This cabling is known as "mini" cable. Leading from the backbone to each device are 3-amp cables called "micro" cables. Red, blue and proprietary connectors, depending on network manufacturer, connect each device, with adapters to integrate these devices into existing networks. System cabling and terminations should always be covered in a thin coat of lithium grease to prevent corrosion, and they should never be placed in a submerged environment. Each component in a DeviceNet system must also be protected with a 3-amp fuse.
4Proprietary Systems: Various companies provide systems for vessels that are similar to aftermarket networks, while still adhering to NMEA 2000 standards. However, adding new aftermarket devices to these existing networks typically requires the use of adapters, since the connectors are usually slightly different. Instead of generic "NMEA 2000" designations, these pre-installed networks usually have specialized names such as SimNet, Seatalk or Dataline 2000 to differentiate themselves in the marketplace.