Merlin-3103 LTE cellular router in critical industrial systems: reliability and security

Mobile data connectivity has reached locations where fixed cabling has never been an option. Pumping stations, solar parks, substations and remote monitoring sites increasingly depend on a connection that is continuous and reliable.

This is exactly where a common mistake is often made – choosing a device that is suitable for an office, not for an industrial environment.

The environment matters more than it may seem

The first thing to consider is the environment. If a device must operate outdoors or in a technical room where temperatures fluctuate, humidity is high and vibration is part of daily life, a “standard 4G router” is no longer sufficient.

Industrial-grade devices such as the Merlin-3103 are designed to operate in temperatures ranging from –40 to +70 °C, without fans or moving parts. In practice, this means fewer failures and a longer service life.

Installation and management – where time (and nerves) are lost

The second key factor is installation and management. Once a project grows beyond just a few sites, manually configuring each router quickly becomes a problem.

Zero-touch deployment is no longer a convenience – it is a necessity. A device that can register itself on the network, download the correct configuration and establish VPN connections without on-site intervention saves both time and frustration. This is one of the core strengths of the Merlin series, which was designed from the outset for large-scale, distributed deployments.

Security must not be an afterthought

Thirdly, security cannot be overlooked. Remote management always increases the attack surface.

In lower-cost devices, security is often limited to a software firewall or VPN. In critical applications, this is not enough. Hardware-based security mechanisms such as Secure Boot and a TPM chip ensure that the device boots only manufacturer-signed software and that cryptographic keys cannot simply be copied. This is especially important when the device is installed in a physically unprotected location.

Origin and lifecycle – a quiet but critical topic

The origin and lifecycle of a device are often underestimated. When hardware, software and manufacturing are sourced from multiple third parties, control is quickly lost.

Merlin is designed and manufactured by a single team, including the operating system and security processes. This provides better traceability, longer product support and fewer unpleasant surprises years down the line.

More than just an “internet router”

Finally, it is worth considering what the device actually does. Is it merely providing connectivity, or can it also function as an industrial protocol gateway – a bridge between legacy automation systems and modern IP networks?

With two Gigabit Ethernet ports and LTE Cat-4 connectivity, the Merlin-3103 can fulfil multiple roles at once, reducing the number of devices required on site and simplifying the overall solution.

Westermo Merlin-3103 – designed for real industrial use, not an office desk

Datasheet: Merlin 3100 datasheet

The Merlin-3103 is compact, yet unmistakably industrial. Its aluminium enclosure, fanless convection cooling and wide operating temperature range of –40 to +70 °C make it suitable for environments where standard routers quickly reach their limits. Typical application areas include:

• pumping stations and water management

• solar and wind parks

• substations and smart grid applications

• remote monitoring and control systems

• industrial automation and SCADA connectivity

Lower-cost routers may work perfectly well in warehouses or server rooms, but in outdoor conditions – vibration, humidity, heat and cold – they tend to fail much sooner. Merlin is designed specifically with these harsh environments in mind.

Zero-touch deployment – no need to handle devices manually

Once projects go beyond a handful of installations, manual configuration becomes a waste of time and a source of errors. The Merlin-3103 works with the Activator Zero Touch Deployment solution, allowing devices to be deployed without on-site configuration. In practice, this means:

• the device arrives factory-prepared

• cellular connectivity is configured according to the order, using a physical SIM card or a project-specific eSIM solution

• once powered on, the device registers itself automatically

• configuration, VPNs and security policies are downloaded remotely

This provides a clear advantage over lower-end devices that require hands-on configuration for every unit.

Security that is not an add-on

Many LTE routers offer security only at a software level. Merlin is built on the principle that security must be part of the architecture, not an optional feature. Key elements include:

• Secure Boot, ensuring the device runs only manufacturer-signed software

• a Trusted Platform Module (TPM) for hardware-based protection of cryptographic keys

• IPSec, VPNs, 802.1X and a stateful firewall included as standard

This is especially important in critical infrastructure, where physical access to devices cannot always be fully controlled.

Stable connectivity and flexibility

The Merlin-3103 is not just an “internet router”, but a multi-purpose industrial communication gateway. It offers LTE Cat-4 cellular connectivity, two Gigabit Ethernet ports and support for industrial protocol gateway and conversion functions.

This makes it possible to connect legacy industrial automation systems to modern IP networks using a single device.

Why it stands out from lower-cost alternatives

The difference is not just in technical specifications, but in philosophy. Merlin is designed for long service life and reliability:

• MTBF exceeding 1.5 million hours

• hardware, operating system and mechanical design developed by a single manufacturer

• manufacturing and secure final assembly carried out in Europe

• not a generic “black box” ODM solution

A low-cost router may work today, but Merlin is designed to keep working five or ten years from now, without the need for constant site visits.

In summary

The Merlin-3103-T2G-QFR-G-DCi0936 is not a compromise. It is a deliberate choice for applications where connectivity is part of critical infrastructure. When you are remotely controlling a pump, inverter or substation, you are not looking for the cheapest solution – you are looking for the most reliable one. And this is exactly where Merlin proves its strength.

Merlin 3103 product card: Westermo Merlin-3103-T2G-QFR-G-DCi0936 – Traadita võrgu seadmed | Electrobit