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The JRC JLN-741A is an IMO type-approved, dual-axis Doppler Speed Log designed for commercial vessels of 50,000 GT and above (such as large tankers, bulkers, and container ships) requiring precise Speed Through Water (STW) measurement in both longitudinal (fore/aft) and transverse (port/starboard) axes.
The “A” model designation denotes the 4-unit expanded architecture, which incorporates a dedicated Distribution Processor unit (NQA-7040) alongside the signal processor, main display, and transducer. This ensures ample NMEA serial and analog outputs for dual-ECDIS, dual-Radar, VDR, Track Control Systems, and multiple berthing display repeaters.
Dual-Axis Speed Tracking: Measures both longitudinal (fore/aft) and transverse (port/starboard) speed components to provide complete movement vectors essential for docking and low-speed maneuvering of large vessels.
Dual-Beam 2 MHz Doppler Engine: High-frequency pulse Doppler beam processing delivers rapid speed updates with exceptional stability ($\pm 0.03\text{ knots}$ at constant speeds).
Integrated Bubble Detection: Real-time signal monitoring checks transducer face contact and flags warnings if aerated water/hull bubbles interfere with speed tracking.
4-Unit Expanded Architecture (Model A): Includes the NQA-7040 Distribution Processor, providing up to 8 NMEA serial channels, analog voltage, and contact closure outputs across the bridge network.
Color Touch Screen Interface: Features the NWZ-510SDW 5.1-inch color touch-panel LCD display with customizable day/night color palettes and intuitive menu structures.
JRC RMS Ready: Connects via LAN to JRC’s Remote Maintenance System (RMS) for automated health diagnostics and preventative maintenance logging.
| Category | Component / Feature | Technical Specification |
| System Model | Model Identifier | JRC JLN-741A (4-Unit Dual-Axis System) |
| Measuring Principle | System Type | Dual-Axis 2 MHz Pulse Doppler Speed Log (Speed Through Water) |
| Measurement Axes | Longitudinal (Fore / Aft) & Transverse (Port / Starboard) | |
| Speed Measurement Range |
• Fore / Aft: -10.00 to +40.00 knots • Port / Starboard: -9.99 to +9.99 knots |
|
| Depth Below Transducer | Effective measuring depth $\ge$ 3.0 meters below transducer face | |
| Speed Accuracy | $\pm 1\%$ or $\pm 0.1$ knots (whichever is greater) / $\pm 0.03\text{ kn}$ stability | |
| Distance Accuracy | $\pm 1\%$ or $\pm 0.1$ NM/hour | |
| Display & Controls | Main Display Unit | NWZ-510SDW (5.1″ Color LCD, 480 x 800 resolution with Touch Panel) |
| Sailing Display Range | 0 to 999,999.99 NM (Model A extended range) | |
| System Units (4-Unit Set) | Core Modules |
1. Main Display (NWZ-510SDW) 2. Distribution Processor (NQA-7040) 3. Signal Processor (NJC-70S) 4. Transducer Unit (Flat type NKF-547 or Gate Valve type) |
| Interfaces & Connectivity | NMEA Output Ports | 8 x IEC 61162-1 / NMEA 0183 Outputs (VBW, VLW sentences) |
| NMEA Input Ports | 1 x IEC 61162-1 GPS Input (RMC, ZDA) | |
| Analog Outputs | 2 x Analog Speed Voltage Outputs | |
| Pulse Outputs | 2 x Contact Closure Log Pulse Ports (200 pulses/NM) | |
| Network & Remote Ports | 1 x LAN Port (JRC RMS Support), 2 x Remote Display Ports (NWZ-650SDR / NWZ-840SDR) | |
| Contact Relay Alarms | Power Fail, Speed Out of Range, and System Fail relay contacts | |
| Electrical & Physical | Power Supply Input | 100 / 230V AC $\pm 10\%$ (50/60 Hz) |
| Power Consumption | $\le 50\text{ W}$ (60 VA at 100V / 150 VA at 230V) | |
| Operating Temperature | -15°C to +55°C | |
| Standards & Approvals | Certifications | IMO MSC.96(72) Compliant, MED Wheelmark, IEC 61023, IEC 60945 |
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