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Analogue Heading Repeaters NT920 AHR (MKI & MKII)

  • Navitron Analogue Heading Repeaters type NT920AHR may be configured as single or multi head independent systems or as add on components to most Navitron autopilot types and Navitron Heading Data Interfaces to display NMEA 0183 heading data received from primary transmission sources of all kinds (Gyro Compass, GPS Antenna Compass, TMC systems etc.)

    Location Note: Standard production units supplied from Serial N° 931899 (June 2002) onwards are of splashproof construction via sealed aluminium case and bezel housings to permit mounting in external locations.

  • Simple to install featuring fully automatic self alignment and self test facilities, all NT920AHR heads are supplied for panel or foot bracket mounting in sheltered locations (enclosed bridge or wheelhouse etc.) unless constructed to latest build standards (see Location Note)

    Ships head is clearly read from a 120mm diameter rotating card marked in 1° increments with 5° and 10° divisions also defined. All 3 digit numbers (4mm height) are shown at 10° intervals and all scale markings are white on a black card background.

    Variable intensity backlight illumination is controlled from a dimmer pot mounted on the instrument bezel to illuminate all card legends in red or green (installation selectable) for night viewing.

  • Unaffected by steel enclosures, the NT920AHR is particularly suitable for emergency steering position use in tiller flats etc.

Autopilot Type NT921 MKII

  • Specifically designed for small professional vessel use (typically 11-20m LOA) the NT921 MKII Autopilot provides a powerful combination of steering system control and interface facilities based on an extremely intelligent Control Unit which is clearly marked and simple to operate.

  • Accordingly, the NT921 MKII offers Navitron steering expertise in a robust and compact package which includes the following special features:

    • Dual Channel Heading Inputs: NMEA 0183 Direct and Mag Sensor Coil
    • Built in Radio Navigator Interface for selectable (HI and LO) automatic track steering between waypoints.
    • Fully automatic stability compensation for variations in rudder speed.
    • Three Heading output Channels for Radar Stabilisation etc. (NMEA, Furuno & Step by Step)

    Standard Features:

    • Full P.I.D Intelligence,
    • Servo driven Heading Repeater (Standby mode),
    • Dual Course Setting and Steer on Lock on facility,
    • Full Automatic Permanent Helm,
    • Digital displays of Heading, Rudder Angle and Cross Track Error (CTE),
    • Operator variable control panel illumination,
    • 11-40Vdc Power Supply compatibility,
    • Solid State Output stages. (11-40Vdc/5A max),
    • Full range menu driven installation presets.
  • Straightforward operation is a key feature of the NT921 MKII thus operator controls are kept to a minimum and are clearly identified by control panel markings which are red backlit for night viewing via a variable intensity illumination control.

    A conventionally marked Course Selector permits simple course selection which is automatically corrected to maintain the vessel on a specified track when connected to a GPS or Track Plotter programmed with a track based on predetermined waypoints.

    Suitable for console or bracket mounting, the NT921 MKII Control Unit is intended for wheelhouse location and is supplied complete with Heading Sensor Coil and Rudder Reference Unit for installation to solenoid hydraulic systems (11-40Vdc/5A max).

    Optional Equipment:

    • Rudder Indicators,
    • Power Steer Controls,
    • Off Course Alarm,
    • Watch Alarm,
    • Universal Relay Box,
    • Analogue Steering Interface,
    • Dual Steering Interface,
    • Bowthruster Interface.

Digital (DHR) Heading Repeater NT920DHR / 2

  • The NT920DHR / 2 Digital Heading Repeater is Type Approved (National Certification by UK Notified Body QinetiQ) for Gyro Compass or THD (etc) Repeater use and is immediately compatible with NMEA 0183 heading data. It is equipped with an opto isolated input port for direct connection to proprietary senders (gyro's, GPS compasses etc.) which transmit one or more of the following sentence types.


  • Ruggedly engineered and suitable for bracket or console mounting in internal and external locations , the NT920DHR / 2 may be installed in single or multihead configurations as add on repeaters with proprietary equipment or to provide an independent system with Navitron equipment such as the NT925OCA / 1 Off Course Alarm. Standard features include a 3 or 4 digit 25mm LCD display of current heading optimised for night viewing by operator variable red backlight illumination.

    Compass Safe Distance - 0.4m

Follow Up & Non Follow Up Power Steer Controls

  • Navitron Power Steer controls are intended for installation in sheltered (bridge or wheelhouse) locations and are suitable for use as single or multistation units with all Navitron autopilot types.

    Fully Type Approved for inclusion in NT921G/951G and NT990G/991G MK2 Autopilot Systems, the NT920NFU is a dual function device which enables permanent (NFU) and temporary (DODGE) heading changes to be ordered at locations remote from the autopilot control unit.

    When set to the DODGE mode, movement of the sprung to centre jog lever produces a fixed amount of Port or Stbd rudder (as appropriate) to turn the vessel. When the jog lever is released to centre, the applied rudder is removed and the vessel returns to the original heading.

    When NFU is selected, the autopilot course setter is automatically switched to a 'tracking' mode. Subsequent movement of the jog lever produces a turn to Port or Stbd (as appropriate) which is 'tracked' by the course setter card as the vessel is power steered to a new heading. When the required new heading is attained and the NT920NFU switch is set to DODGE or OFF, the autopilot course setter card immediately 'locks' and the autopilot resumes control to maintain the vessel on the new (current) heading.

  • The NT990FU (Follow Up) Control is also Type Approved for use with NT951G/NT991G MK2 Autopilot systems and enables permanent (POWER STEER) heading changes to be ordered at locations remote from the autopilot control unit.

    The direction of movement of the NT990FU lever (right or left) to initiate Port or Starboard rudder movement is installation selectable and automatically Corresponding coloured sectors results in reversal of the corresponding red and green sectors on the control panel. This is achieved by bi-colour backlighting which is variable via the ILLUM key.

    Two installation programmable modes are available to the operator via the RANGE key. Range 1 can, for Range Keyexample, provide linear ± 40° rudder movement for normal operating use whilst Range 2 can be customised to suit special work requirements (alternative rudder angles, linear or non linear)

    When the NT990FU is engaged (ON) and the vessel is power steered to a new heading by this means, the autopilot course setter card 'tracks' ships head. On attainment of the new heading required, the NT990FU key can be set to OFF at which time the course setter card automatically 'locks' and the autopilot immediately resumes control to maintain the vessel on the new (current) heading.

  • Identical in function to the fixed station NT920FU the Navitron Hand Held Remote Steer Control type NT920HRC is fitted with a 3 metre length of trailing cable to provide portable follow up power steer control.

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.

  • 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.

  • 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.

  • NT880 Dimensios
  • NT990 Dimensios

Heading / Speed Data Interfaces Type NT920HDI

  • The NT920HDI converts serial heading data received from different types of proprietary heading transmission sources (electronic compasses including GPS antenna types etc.) to the data type required by various end user brands of radars, trackplotters and heading repeaters etc. including some Navitron autopilot types. In addition, NT920HDI software version 4.0 onwards incorporates speed log pulse input facilities which are combined with heading to provide NMEA output data (VHW sentence) for use by ECDIS etc.

  • The input signal applied to the NT920HDI can be of a single type (NMEA only or Furuno only) and will result in simultaneous output transmissions.

    Alternatively more than one heading input signal type can be simultaneously applied in which case the priority (preferred) input data to be accepted is installation selectable with backup (2nd choice) data immediately available in the event of principal data failure.

    If the priority input data fails, the NT920HDI will automatically select the 2nd source after a period of 5 seconds and will automatically revert to the preferred source as soon as data is restored.

  • When speed log input data is also available, this will automatically be combined with the heading output data to provide NMEA outputs in the VHW sentence format required by ECDIS etc.

    The NMEA and Furuno outputs are not opto isolated and require that the associated receiver units are themselves equipped with opto isolated input stages to avoid common mode problems.

    The Step by Step output is installation selectable at 3, 6, 12 or 24 steps/degree (as required) and is logic rated at 5V p.p / 2mA per step line and will in many cases require buffering with a Navitron Step Interface Box type NT925SIB.

  • Typically for use with electronic compass types including GPS antenna models and / or pulse output speed logs

Heading / Speed Data Interfaces Type NT921HDI

  • The NT921HDI is available in two forms to convert Sin/Cos Heading signals received from proprietary compasses / fluxgate devices etc. to standard NMEA heading data. The resultant serial data accords with IEC 61162/1 and IEC 61162/2 (as preferred) and can be used as a heading input to a Navitron Autopilot System or for inputs to other proprietary equipment such as radar (stabilisation) or ECDIS etc.

  • This is the simpler form of interface which can be connected within a Navitron Autopilot System and uses the regulated power supplies available from the Autopilot Control Unit as it's power source.

    The PIC processor intelligent NT921HDI then decodes applied Sin/Cos Heading signal and converts the input signal to NMEA 0183 serial output data which is installation selectable for 4800 or 38400 baud and update rates of 1Hz or 10Hz as required.

  • This is the stand alone version of the Sin/Cos to NMEA converter and is suitable for direct connection to 11-40Vdc vessel power supply as voltage regulation is included in the NT921HDI/2 (Type 2).

    The single channel NMEA 0183 Heading data output signal is opto isolated to eradicate common mode problems and provides installation selectable update rates of 1Hz, 10Hz or 20Hz dependent upon the output baud rate selected (4800 or 38400).

  • For Sin / Cos compass to NMEA data.

Heading / Speed Data Interfaces Type NT922HDI

  • The NT922HDI provides conversion functions from NMEA Heading data to 5Vp/p Step by Step and from single channel NMEA Heading data to dual channel opto isolated NMEA outputs which are independently selectable to provide both baud rate and update rate conversions.

  • The NT922HDI NMEA serial data outputs are available in two sentence types ($XXHDT or $XXHDG) which are derived and reliant upon the input data received.

    The outputs (opto isolated) can be connected to external "listeners" in RS422, RS232 and standard NMEA connection formats.

    The input signal applied to the NT922HDI can be of a single type NMEA only

  • Suitable for stand alone 11-40Vdc power supply operation, the NT922HDI can be used in buffered NMEA to step repeater applications etc. and the baud rate conversion function provides a simple solution to many interfacing requirements involving equipment from different systems operating at different baud rates.

Heading / Speed Data Interfaces Type NT923HDI

  • Suitable for stand alone (independent system) use, the NT923HDI (Heading Data Interface) provides two channels of 10Hz NMEA 0183 heading output data and one Navitron serial output derived from a Navitron Heading Sensor Coil (HSC1 or HSC2) mounted above or below a good quality externally gymballed ships magnetic compass.

  • The magnetic information received from the compass via the Heading Sensor Coil can be electronically corrected for deviation during installation and the resultant heading permanently displayed and transmitted at a fixed 10Hz update rate in the following NMEA sentence types (from software version 2.0 onwards) : $HCHDT, $HCHDM.

    Both sentences include checksum and are continuously transmitted at 10Hz on both NMEA output channels. The output channels are electrically isolated from the Ships supply and opto isolated to eliminate receiving equipment common mode connection problems.

    Built in alarm functions triggered by internal monitors warn of magnetic data (input signal) and NMEA output data failure.

    An internal power monitor relay provides a volt free normally open (NO) or normally closed (NC) contact to warn of power supply failure (contact ratings 0.5A @ 125Vac, 1A @ 30Vdc).

    Suitable for 11 - 40Vdc power supply connection, the NT923HDI can be powered up directly via its panel mounted ON/OFF switch or from a remote location via remote power up terminals provided.

  • Suitable for 11 - 40Vdc power supply connection, the NT923HDI can be powered up directly via its panel mounted ON/OFF switch or from a remote location via remote power up terminals provided.

Heading / Speed Data Interfaces Type NT925HDI

  • BSH Type Approved for stand alone (independent system) use with azimuth tracking units of all kinds (radars, trackplotters, antenna alignment systems, nav computers etc.) and Wheelmark approved for use with Navitron NT921G/NT951G/NT990G and NT991G MK2 autopilot systems, the NT925HDI (Heading Data Interface) provides four types of simultaneous output data converted from virtually any synchro or step by step gyrocompass heading outputs.

  • In addition, NT925HDI units incorporating software version 2.0r and later, will accept 200 or 400 pulses per nautical mile from speed log systems and will provide NMEA output data in heading only, speed only or combined speed and heading formats as required by ECDIS and AIS Systems etc. Version 3.0 software and later also provides Rate of Turn (ROT) NMEA data outputs.

    On receipt of gyro heading signals, all four data types are simultaneously and continuously transmitted on the relevant output channels which are opto isolated to eliminate common mode complications.

    When speed input data is available (200 or 400 pp.nm) combined speed and heading data is also available from the NMEA output channels (VHW sentence)

    Gyro heading data is permanently displayed on the NT925HDI via a 4 digit LCD with variable red backlight illumination for night viewing and built in alarm functions warn of gyro input and / or NMEA output data failure.

    An internal power monitor relay provides a volt free normally open (NO) or normally closed (NC) contact to warn of power supply failure (contact ratings 0.5A @ 125Vac, 1A @ 30Vdc).

  • Suitable for 11 - 40Vdc power supply connection, the NT925HDI can be powered up directly via its panel mounted ON/OFF switch or from a remote location via remote power up terminals provided.

Heading / Speed Data Interfaces Type NT990HDI

  • BSH (Germany) type approved for AIS, ECDIS, Radar and Heading Repeater interfacing, the NT990HDI (Heading Data Interface) will convert virtually any Synchro or Step by Step heading input signal to heading data transmitted on 1 (NT990HDI/1) or 2 (NT990HDI/2) isolated NMEA 0183 output channels. The output channels may be independently set for IEC 61162/1 (4800 baud) or IEC 61162/2 (38400 baud).

  • A speed log giving 200 or 400 ppNm may also be connected to the NT990HDI to provide NMEA 0183 speed information to proprietary systems.

    All inputs to the NT990HDI are Opto-Isolated to eliminate common mode and loading problems.

    The NMEA 0183 output sentences may be set for heading only ($HEHDT), heading and Rate Of Turn ($HEROT), heading and speed ($VDVHW) or heading, rate of turn and speed.

    Heading information is permanently displayed on a 4-digit LED display with variable intensity for night viewing whilst built in alarm functions triggered by internal monitors warn of heading input or NMEA output failure.

    An internal power-monitoring relay provides a volt free normally open (N.O.) or normally closed (N.C.) contact to warn of power supply failure. Contact rating 1A@30Vdc

  • Suitable for 11-40Vdc power supply connection, the NT990HDI may be powered up via the unit mounted ON/OFF keypad or from a remote location via remote power up terminals also provided.

Navitron NT990BNWAS

  • Bridge Navigational Watch Alarm System

    Fully compliant with IMO Resolution MSC.128(75) & IEC 62616 and with both Notified Body (Germanischer Lloyd) & Classification Society (RMRS & CCS) Type Approvals, the Navitron NT990BNWAS can be supplied as a basic system to operate proprietary alarm units (where appropiate) or, as an expanded system complete with alarm selector switch and individual officer cabin and crew call audible alarm units etc. In either case, the NT990BNWAS provides a safety monitor requiring regular acknowledgement (Reset) by the duty watch personnel at time intervals between 3 and 12 minutes which can be specified and set by the master or OOW as considered appropriate.

  • The chosen time interval (3 - 12 mins) is security protected by means of key switch selection as is the operating mode which may be set:

    • Permanently ON

    • Permanently OFF

    • AUTO mode (automatically activated by power up of other equipment such as Autopilot / Track Control system etc)

    Once activated, completion of the specified timeout period (3 - 12 mins) will automatically generate a Bridge visual alarm (15 secs) followed by a Bridge audible alarm (15 secs) which is tone and volume adjustable during installation.

    Alarm cancellation and commencement of a new timing period will occur whenever the BNWAS 'Reset' button is operated on the main unit or when other Wheelhouse / Bridge located Resets (or optional Movement Detectors) are activated.

    Failure to 'Reset' the system during the 30 second Bridge visual / audible alarm period will result in automatic 'Officer Call' alarm activation which, in an expanded system, can be routed to the appropriate duty officer cabin alarm unit. If the officer call alarm stage is not acknowledged within a selectable 90 sec to 3 minute period, a final stage Crew Call will automatically be generated.

  • In the event of a sudden crisis situation requiring immediate Officer assistance, the NT990BNWAS also features an 'Emergency Call' facility which may be operated at any stage of the timing cycles.

    Further built in security and error management provisions include 'Tamper' and 'Power Fail' alarm indications fully commensurate with MSC.128(75) and IEC 62616.

    The NT990BNWAS is suitable for vessels of all types and tonnages and can be supplied for both 115 / 230 VAC (DB2) and 24 Vdc (DB1) power supply applications.

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Off Course Alarm Type NT925OCA

  • The Navitron Off Course Alarm type NT925OCA is a fully independent course monitoring device which complies with the articles of IMO resolution A342 (IX).

    It can be installed with a single heading input obtained from a Navitron Heading Sensor Coil (type HSC2) or from a proprietary NMEA source (or both) when used as a completely independent system. However, if one of the heading data inputs is common to the heading data provided for an autopilot system (gyro data etc) the second heading input to the NT925OCA must be obtained from an independent (mag compass etc) source.

  • NT925OCA / 1 is primarily intended for use as an independently referenced course monitor which, when installed as an independent system or in conjunction with an appropriate Navitron Autopilot system, renders the entire configuration compliant with all articles of IMO Resolution A.342(ix).

    Dual Heading input ports are standard and can be connected to accept magnetic information derived from a Navitron heading sensor coil attached above or below an existing ships compass and / or a range of NMEA 0183 heading sentences derived from proprietary sources such as GPS compasses and Gyro’s etc. Whilst only one heading input is essential, dual inputs will provide a back up system where either input maybe chosen as the primary or secondary heading reference.

    Standard features include installation programmable Deviation and Variation correction, NMEA 0183 and Step by Step (installation Programmable 3, 6,12 and 24 step/degree) heading outputs for use by proprietary radars etc.

  • NT925OCA / 2 is designed for use as an independently referenced Off Course Alarm but includes a Course Comparator Alarm which may be enabled or disabled during installation as required.

    Unlike the heading sensor coil and single NMEA input associated with the NT925OCA / 1, the NT925OCA / 2 features dual NMEA 0183 heading input ports. Only one input is required for Off Course Alarm operation whilst dual inputs are essential for the additional Course Comparator function which continuously monitors and compares the two sets of NMEA data received. In the event of excessive differences between the data received (trip level installation programmable 1-20°) the alarm is activated.

Rudder Angle Indicator Type NT850RAI & NT1000RAI

  • The NT850 and NT1000 RAIs are Class (GL) Type Approved for Steering System use and are also "Wheelmarked" (MED Module B) as compliant with ISO 20673 (2007).

    Suitable for nominal 24Vdc supply (11-40Vdc) the indicators will accept potentiometric and serial data ($xxRSA) inputs of rudder angle signalled by Navitron Systems Ltd. or suitable proprietary Rudder Reference Units.

  • Each Indicator Head is processor intelligent and can be individually calibrated for amidships, full scale and linearity.

    Variable scale illumination via an external control voltage or locally mounted potentiometer is also featured for night viewing.

    Dual Rudder Reference Units of the NT920 or NT1000 type are required to provide the signal to the RAI to render it electrically independent from the NT850 Steering System.

  • NT850 Dimensios
  • NT1000 Dimensions

Rudder Angle Indicator Type NT920RAI

  • Navitron Rudder Angle Indicators (type NT920RAI) can be configured for single or multi head display as add on components to all Navitron autopilot types or as independent (stand alone) systems employing a dedicated Rudder Angle Transmitter Unit (NT920RTU).

  • All Indicator heads (NT920RAI) are electrically and mechanically identical (no master / slave distinction) which provides complete interchangeability and straightforward system expansion.

    Each Indicator head comprises a robust centre zero moving coil driving an illuminated white pointer against a black scale background graduated in 5° increments. Provision is also made for fixed and variable intensity red backlight scale illumination for night viewing.

  • Standard RAI heads are suitable for wheelhouse (sheltered) panel mounting. External locations may be used (foot bracket or panel mount) when supplied with a Navitron Pod assembly (PM).

    Compass Safe Distance - 1.0m

    Weight NT920RAI Standard - 370g

    Weight NT920RAI (PM) - 1.1Kg

Watch Alarm Type NT920WA

  • Unsuitable for external location, the Watch Alarm should be installed in an enclosed bridge or wheelhouse in a position commensurate with RESET button operation.

  • At the instant of autopilot engagement (Mode switch to ON) a four minute timing period commences which may be restarted at any time by manual operation of the Watch Alarm RESET button.

    If the RESET button is not pushed and the four minute period expires, a low level audible alarm is emitted for a period of one minute (60 seconds).

    Failure to cancel the low level alarm within 60 seconds will result in a high level audible alarm which will continue until the RESET button is operated (new four minute period starts) or until the autopilot is disengaged (Mode switch to STANDBY or OFF).

  • A two way built in POWER FAIL alarm will immediately sound at the emergency high level in the event of autopilot power supply or watch alarm internal battery failure.

    The POWER FAIL alarm can only be reset by disengagement of the autopilot or restoration of the power supply.

    A volt free normally open contact rated 1A / 24Vdc is provided within the Watch Alarm to drive an auxiliary alarm (if required) in the high level (emergency) mode only.

    Compass Safe Distance - 1.0m

    Weight - 1.0Kg

  • Navitron