According to the specification, an NMEA 2000 network has two terminators (120-Ohm resistors) connected to the NMEA 2000 backbone endpoints. Device models with the T index at the end of their names contain a built-in terminator and should be connected to the network instead of the terminator. This allows zero-cost connection of the Devices to existing networks that have no free connectors. Sometimes it is hard to find the end of the bus and terminator on large vessels.