The Wlink RT600 is a compact cellular RTU that brings legacy serial and analog field devices onto a 4G/3G/2G IP network without replacing existing sensors or PLCs. One RS-232 port connects to a local configuration laptop; one RS-485 port polls Modbus RTU slaves such as flow meters or energy meters; two analog inputs accept 4-20 mA or 0-5 V signals from temperature, pressure, or humidity transmitters; two digital inputs monitor dry contacts from door sensors, smoke detectors, or pump status relays. All collected data is timestamped with the built‑in RTC and pushed to the central SCADA or cloud platform via MQTT, TCP, UDP, or SMS—selectable per channel and per alarm condition. The RT600 is programmable: users can customize DI/AI thresholds, Modbus register maps, and JSON payload structure to match legacy master protocols without writing firmware.

When the Fiber Cuts — SMS and Auto-Reconnect

• Multi‑Path Failover: In normal operation the RT600 streams data to a fixed IP or dynamic DNS data center over TCP or UDP. If the cellular data session drops—due to carrier maintenance, SIM card credit exhaustion, or a base station failure—the device automatically falls back to SMS mode, transmitting critical alarm messages as short texts to a predefined phone number. Once the data session is re‑established, it resumes IP transmission without manual intervention, with a user‑definable reconnect interval.
• Always‑Online / Idle / Command Modes: Three power profiles match different field conditions. Always‑online mode keeps the modem connected continuously for low‑latency SCADA polling. Idle mode disconnects the modem and re‑activates it only when triggered by user data, an incoming ring, or an SMS command—reducing power consumption for solar‑powered sites. Command mode allows the master to remotely toggle the RT600 between online and offline states via SMS or a serial AT command.
• Heartbeat and Link Monitoring: A user‑defined heartbeat frame is sent at configurable intervals. If the master fails to receive the heartbeat within the expected window, it knows the RTU or the network path is down—before any process alarm is missed. Combined with LED status indication on the front panel, field technicians can visually verify power, network registration, and data activity without a laptop.

Field Wiring, Power, and Programmability

• Wide‑Range Power Supply (7.5–32 VDC): The RT600 accepts any DC voltage between 7.5 and 32 V. It can be powered from a 12 V battery, a 24 V control panel supply, or a solar charge controller without an intermediate DC‑DC converter. External power on/off control via a dedicated pin allows a watchdog timer or external relay to hard‑reset the device.
• Industrial Pluggable Terminal Block: All I/O and power connections use a single industrial‑grade pluggable screw terminal block. The pinout is laser‑printed on the housing: V+, GND, RS‑485 B/A, RS‑232 GND/RX/TX, DI1+, DI2+, DI GND, AI1+, AI2+. A technician with a flat‑blade screwdriver can wire a complete monitoring station—temperature sensor, door switch, and Modbus flow meter—in under fifteen minutes, then verify each channel via the LED status indicators before leaving the site.
• Programmable Logic Without a PLC: Through the PC‑based RTU Configuration Tool or remote SMS commands, users can map AI threshold violations to specific SMS recipients, change Modbus register polling sequences, or define custom JSON payloads. This shifts basic edge logic from the central SCADA to the RTU itself, reducing cellular data consumption and ensuring that local alarms are raised even when the IP link is down.
• GPS Optional: For mobile assets—refrigerated trucks, rail wagons, construction site generators—an optional GPS receiver adds latitude, longitude, and speed to each data frame, enabling track‑and‑trace alongside temperature or fuel‑level monitoring.

Applications

• Cold chain logistics: trailer‑mounted temperature and door‑open monitoring with GPS tracking
• Oil and gas: remote tank level and pressure monitoring at unmanned wellheads via Modbus and 4‑20 mA
• Water and wastewater: pump station status, flow meter reading, and chlorine residual monitoring over SMS
• Power distribution: ring main unit (RMU) status and transformer temperature monitoring for utilities
• Environmental monitoring: river level, rainfall, and air quality stations in flood‑prone areas
• Streetlight and tunnel lighting control via digital output and Modbus commands
• Any SCADA application where legacy serial and analog sensors must be brought onto a cellular IP network without replacing field hardware