Garmin TR-1 Marine Instruments User Manual

The TR-1 Autopilot is designed in conformance with the NMEA 0183 standard. The TR-1 will
communicate reliably and safely when connected to other devices that meet this standard with the
normal wire connections. Some manufacturers imply that they conform to the standard when in fact
they do not. Any device that requires a signal connection to ships ground is not in compliance
with the standard. The installer needs to conrm that connections to non-compliant devices are wired
in a fashion to ensure a safe and effective connection. In these cases the following procedure shall be
An indication that a device may be a non-compliant device is that the GPS signal is accepted by the
TR-1, but the RADAR shows no heading data, or has an intermittent heading input signal.
When connecting the NMEA heading output to a non-compliant NMEA device, the NMEA positive
signal from the TR-1 shall be connected to the receiver NMEA positive signal. The connection should
then be tested to see if communications have been established, that is to say, does the intended receiver
indicate that valid heading data is being received from the TR-1. If so then no other connections need
to be made.
If the data is not being received by the receiving device, try to connect the receiving device power
ground to the same power ground as the TR-1.
If this cannot be done, a last resort is to connect the power ground of the receiver to the green wire
ground connection of the TR-1 NMEA interface wires through a 125mA inline fuse. It is VERY
important that the grounds never be connected without the fuse as this can create a re hazard
in the boat. Please contact TR-1 Autopilots technical support at 1-866-559-0229
for assistance.
When connecting the TR-1 NMEA input to a non-compliant device there should be no problem as
the NMEA standard allows this connection to be made safely, although in this case ground noise may
show up on the signal and cause intermittent problems. If these problems are experienced, a possible
solution is to be certain that the “signal ground” and the power ground are connected at the same
Non-Compliant NMEA 0183 Devices