• overview

RLTK421 Industrial 4G/LTE VPN Router

Compact, rugged 4G/LTE router with 2× Ethernet (LAN/WAN), Wi-Fi hotspot, and RS-485/RS-232 for secure PLC/HMI remote access. Built for industrial IoT, it delivers fast LTE with plug-and-play setup via a simple web UI; Linux-based firmware adds flexibility, while surge/ESD protection and a hardware watchdog keep it stable 24/7 in harsh sites.

Connectivity & Interfaces

4G/LTE with 2× Ethernet (LAN/WAN) and a Wi-Fi hotspot for fast site networking. The RS-485/RS-232 terminal enables transparent serial communication to PLCs/HMIs.

VPN & Security

Encrypted tunnels with OpenVPN, IPsec, L2TP, GRE plus firewall/ACL and DoS protection. LTE/Ethernet failover and auto-reconnect keep connectivity uninterrupted.

Industrial Design & Reliability

Metal enclosure, −20~+70 °C operating range, and DIN-rail/panel mounting for harsh sites. Surge/ESD protection and a hardware watchdog ensure reliable 24/7 operation.

  • Why RLTK421

Key Features

RLTK421 is built to deliver secure remote access without a site visit. With LTE, multi-VPN, and serial bridging, you can connect to PLCs/HMIs in minutes.

  • 4G/LTE with Auto-APN — Fast bring-up and auto-reconnect to keep sites online.
  • Multi-VPN (OpenVPN / IPsec / L2TP / GRE) — Secure tunnels for interoperable remote access.
  • 2× Ethernet (LAN/WAN) + Wi-Fi Hotspot — Connect field devices and users in minutes.
  • RS-485 / RS-232 Bridging — Transparent serial communication to PLCs/HMIs; Modbus RTU↔TCP.
  • Rugged Design (−20~+70 °C, Metal, DIN-rail) — Built for harsh industrial environments.
  • Remote Management & Alarms — Web/SSH/SNMP control, email/SMS alerts, hardware watchdog.
  • overview

Technical Highlights

Compact, rugged 4G/LTE router with 2× Ethernet (LAN/WAN), Wi-Fi hotspot, and RS-485/RS-232 for secure PLC/HMI remote access. Built for industrial IoT, it delivers fast LTE with plug-and-play setup via a simple web UI; Linux-based firmware adds flexibility, while surge/ESD protection and a hardware watchdog keep it stable 24/7 in harsh sites.

Cellular
4G/LTE (3G/2G fallback), 1× SIM, SMA antenna
Ethernet
2× RJ45 (1× WAN switchable to LAN + 1× LAN), 10/100 Mbps
Wi-Fi
802.11 b/g/n 2.4 GHz AP / Hotspot
Serial
RS-485 (default) / RS-232, Modbus RTU↔TCP, up to 230.4 kbps
Power
9–36 V DC, typ. ~270 mA @ 12 V
Environment
−20 ~ +70 °C, IP30, DIN-rail / panel mount
Security / VPN
OpenVPN, IPsec, L2TP/PPTP, GRE; firewall/ACL, DoS protection
Certifications
CE / FCC (EMC)
  • Why RLTK421

Ports & I/O

Snapshot of the physical interfaces on RLTK421.

  1. SIM slot: Single SIM tray for LTE.
  2. LTE antenna (SMA): External SMA connector.
  3. Ethernet: 2× RJ45 — WAN (switchable to LAN) + LAN, 10/100 Mbps.
  4. Wi-Fi antenna: 2.4 GHz AP/Hotspot (if present).
  5. Serial terminal: RS-485 (default) / RS-232; Modbus RTU↔TCP.
  6. Power input: 9–36 V DC (terminal or barrel jack).
  7. Ground: Protective earth / GND lug (if present).
  8. Reset & LEDs: Power/LTE/SIM/WAN-LAN indicators.
  • secure remote access

Connect It to RoltekConnect Cloud

With RoltekConnect Cloud, RLTK421 joins a zero-trust tunnel. Use role/time-based access and session auditing to control who gets in, when, and what they do. Monitor health, push configs and firmware remotely.

  • Solutions

Use Cases

Remote PLC Maintenance

Monitor, troubleshoot and program PLCs/HMIs without a site visit—secure, auditable access via a zero-trust tunnel.

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External Party Access Governance

RoltekConnect Cloud converts external parties access into a temporary, scoped, and fully auditable request → approve → operate flow, eliminating operational risk.

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3. use case

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