Systems Ltd
Gyro/Mag Heading Repeaters
Type NT880 AHR & NT990 AHR

Navitron Analogue Heading Repeater types NT880 AHR & NT990 AHR are Approved and Certificated by Germanischer Lloyd as fully compliant with all aspects of IEC 60945 and may be configured for single or multihead display of NMEA 0183 Heading Data received from proprietary transmission elements (Gyro, TMC systems etc.).

In cases involving non NMEA data sources (proprietary Gyros etc. with step by step or synchro type outputs) an Approved Navitron Heading Data Interface may also be employed for conversion of step/synchro signals to NMEA Serial Data.

Navitron Heading Data Interface types NT990 HDI & NT925 HDI are available for this purpose.

Suitable for 11 – 40Vdc operation, all NT880 AHR Repeater heads are fully interchangeable (no master or slave distinction).

The NT990 AHR heads are also fully interchangeable and both types may be panel or bracket mounted.


Bezel outline dimensions of 192 X 192mm (NT880 AHR) and 240 X 240mm (NT990 AHR) allow the units to be mounted in the appropriate DIN size panel cut outs if required.

A single input is necessary (NMEA heading data in at 4K8 or 38K4 baud) for each Repeater type. Additionally, two power supply inputs (normal and backup) a remote Illumination Control input and a power failure alarm output facility are available with a total of 5 cable entry glands provided.


Both Repeater types are self aligning (no calibration required) thus both the main and inner cards will automatically align with NMEA 0183 data received.

Ships head is simply read from a 150mm diameter (NT880 AHR) or 180mm dia (NT990 AHR) main rotating card which is marked in 1° increments with 5° and 10° divisions also defined. The smaller diameter inner card rotates at a rate which is 10 times faster than the main card to provide a clear indication of tenths of a degree. All 3 digit numbers (4.5 or 5.0mm height) are shown at 10° intervals and all scale markings are white on black card backgrounds.


Variable intensity backlight illumination is controlled from a dimmer pot mounted on the instrument panel(s) or via an external dimmer, to illuminate all card legends in red or green (link installation selectable) for night viewing.

Operational integrity is continuously monitored and both Repeater types provide front panel indications of Heading Data type (True or Mag) and failure status (if appropriate) involving Alignment, Data and Power failure malfunctions. The visual indications are accompanied by an audible alarm which may be silenced when acknowledged by Alarm key operation.

NT880 AHR & NT990 AHR Manual download (PDF)

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