Industrial 4G LTE Cat.1 Cellular Modem (RS232/RS485)

The VT-DTU500C is an industrial 4G LTE Cat.1 DTU that seamlessly extends RS232/RS485 serial loops to cellular networks. It provides native MQTT integration and Modbus RTU to JSON conversion, making it a highly secure, low latency edge node for remote SCADA telemetry.

Part No. VT-DTU500C
sku : IoT-4GD101
INSTANT QUOTE

Valtoris VT-DTU500C Industrial 4G Cellular Modem DTU Overview

LTE Cat-1 Cellular Backhaul

Designed as a reliable 4g cellular modem with sim card slot (Micro SIM), it provides robust cellular backhaul across FDD-LTE, TDD-LTE, and GSM frequency bands, delivering up to 10Mbps downlink and 5Mbps uplink transmission rates with automated 2G GPRS fallback.

4G LTE-FDD TDD and GSM Frequency Band Matrix

Comprehensive IoT Edge Capabilities

Executes transparent serial forwarding, persistent Modbus RTU to Modbus TCP protocol conversion, and automated JSON payload encapsulation directly at the sensing edge.

VT-DTU500C Core Architecture and Protocol Conversion Engine
Automated Modbus RTU to JSON String Encapsulation
Direct MQTT Publish Subscribe Link to Public Cloud Brokers
Multi-Platform Cloud Compatibility AWS Azure AliCloud
Customizable Hex ASCII Registration and Heartbeat Packets

Industrial Grade Hardware Watchdog Circuit Stability

Centralized VirCom Remote Device Management and OTA Upgrades

RS232 & RS485 Interface Definitions

Utilizes reliable 9~24V DC terminal block power inputs and highly insulated serial bus connections to survive extreme cabinet voltage fluctuations.

Valtoris VT-DTU500C Hardware Interface and Port Schematic

Mechanical Dimensions

VT-DTU500C Outline Mechanical Dimensions CAD schematic

Technical Specification | VT-DTU500C
Hardware & Physical Interfaces
Serial Interfaces1× RS232 (DB9 Male) + 1× RS485 (Terminal Block)
Ethernet Port1× RJ45 Port (Reserved expansion port, currently inactive)
Antenna Interface1× Standard 50Ω SMA Female Connector (Cellular RF)
SIM Card ArchitectureMini SIM Card (2FF) – Size: 25mm × 15mm (3V / 1.8V compatible)
Dimensions (L×W×H)9.0 cm × 6.5 cm × 2.5 cm (Native DIN-rail/Wall mount)
Enclosure MaterialSECC Metal (Rugged industrial anti-interference design)
Cellular Network & Speed
Supported ModesFDD-LTE / TDD-LTE / GSM (Automated 2G GPRS fallback)
4G LTE BandsFDD-LTE: B1/B3/B5/B8 | TDD-LTE: B34/B38/B39/B40/B41
2G GSM BandsGSM/GPRS: B3 / B8 (1800 / 900 MHz)
Max Data ThroughputLTE: Max 10Mbps Downlink / Max 5Mbps Uplink
Serial Bus & Software Protocols
Baud Rate Range300 ~ 921600 bps
Core Protocol StackModbus RTU to JSON, Modbus TCP, MQTT client, HTTP POST/GET
Edge ComputingData overrun alarms, register scaling, device offline alert
Device ManagementSerial AT Commands, VirCom Utility, Cloud OTA
Electrical & Environmental
Operating VoltageDC 9V ~ 24V (Q2.1 power socket / Terminal block input optional)
Working CurrentCommunication: 50mA @ 12V | Standby idle: 25mA @ 12V
Op / Storage Temp-40°C ~ +85°C / -45°C ~ +165°C
Operating Humidity5% ~ 95% Relative Humidity (Non-condensing)
High-Speed Cellular Backhaul
✓ Fast LTE Cat.1 Transmission: Achieves speeds up to 10Mbps downlink and 5Mbps uplink, vastly outperforming legacy 2G GPRS modems across industrial telemetry loops.
✓ Automated 2G Fallback: Maintains uninterrupted data logging at remote, off-grid substations by automatically falling back to GSM/GPRS networks when LTE signal coverage is inconsistent.
Core Edge Computing Capabilities
✓ Autonomous Modbus-to-JSON Parsing: Regularly polls Modbus RTU or DLT-645 instruments, and converts registers into elegant HTTP/MQTT JSON strings, avoiding need for costly local edge PCs.
✓ Native MQTT Protocol Integration: MQTT Publish/Subscribe topics, keep-alive timer & authentication keys built-in to seamlessly connect to popular cloud brokers (AWS, Azure, AliCloud)
✓ Embedded Watchdog Protection: Internal hardware watchdog logic continuously monitors system execution, executing zero-touch autonomous restarts if carrier cellular linkage stalls.
Mission-Critical OT Applications
✓ SCADA Modernization: Upgrade serial RS485 polling networks to long-range cellular telemetry without rewriting underlying ladder logic inside existing field PLCs.
✓ Extreme Outdoor Deployments: Operates flawlessly inside unventilated, severe-weather distribution enclosures subjected to ambient temperatures from -40°C to +85°C.
What happens to my Modbus telemetry if the 4G LTE cellular connection temporarily drops?
Blind spots are a reality in industrial environments. The VT-DTU500C features an embedded hardware watchdog circuit and autonomous “Keep-Alive” network testing. If it detects a socket connection loss, it automatically forces the cellular module to re-dial. However, the physical modem does not maintain a massive historical register cache during prolonged outages. If absolute zero-data-loss is mandatory for your remote sensing loops, we strongly suggest installing our Active RS485 Caching Hub upstream of the gateway.
Do I need a dedicated M2M/IoT SIM card, or will a standard commercial data SIM work?
The gateway is completely unlocked and works with all Standard Mini SIM cards (2FF / Size: 25mm × 15mm). It works flawlessly on commercial LTE data plans, private APNs and dedicated M2M IoT SIMs that match its FDD/TDD frequency bands. Note: If you want to configure the modem remotely using serial AT commands via cellular SMS then ensure your SIM data plan has SMS messaging enabled.
Can I write custom Python/Linux scripts inside the modem to pre-process register data?
However, to ensure full operational stability and to avoid memory-leak firmware crashes at the sensing edge, the VT-DTU500C does not run a custom user Linux OS. Instead, its internal VirCom conversion engine autonomously structures your Modbus RTU hex registers into standard, lightweight JSON key/value pairs. This universal payload format can be instantly ingested and mapped by the native payload formatters inside AWS IoT Core, Azure IoT Hub, or AliCloud.
Why does this specific DTU utilize LTE Cat.1 instead of the faster LTE Cat.4?
LTE Cat.1 (10Mbps down / 5Mbps up) is the absolute engineering sweet spot for deterministic SCADA telemetry. While Cat.4 delivers higher raw video streaming bandwidth, it consumes vastly more power and dissipates excessive thermal heat. Cat.1 provides massive overhead for Modbus register frames and MQTT JSON topics while maintaining severe thermal stability across continuous 24/7 operation inside sealed, unventilated outdoor panel enclosures.
Technical Documents
VT-DTU500C Product User Manual
Complete hardware wiring definitions, AT command configurations, and Modbus JSON payload examples.

[ Download PDF Manual ] →

Configuration Utilities
VirCom 7.22 Setup Software (RAR Archive)
Official Windows utility for LAN/Cloud device discovery, virtual serial port binding, and ZLMB gateway routing tables.

[ Download Setup Utility ] →

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