The shutdown of analog and ISDN telephone networks has posed significant challenges to many industrial, technical, and safety-related installations. The AT Modem Emulator from Wiesemann & Theis offers a direct and uncomplicated replacement for classic modems by enabling serial communication via TCP/IP Ethernet – without requiring changes to existing hardware or software.

With virtual COM ports, box-to-box connections, and optional TLS encryption, it provides a secure, future-proof platform that is easy to integrate. Power-over-Ethernet (PoE) ensures flexible powering options, while its rugged industrial-grade design allows for trouble-free 24/7 operation.

1:1 replacement for analog and ISDN modems

The AT Modem Emulator is fully AT command-compatible and pin-compatible with standard modems. Existing RS232 connections can be adopted without modifications. Instead of a telephone number, the IP address or host URL of the target system is specified. This allows previous modem-based connections to be seamlessly switched over to an Ethernet-based communication protocol.

This functionality is especially relevant for applications such as:

• Remote monitoring of climate and cooling systems
• Remote alarming in security systems
• Data acquisition in measurement technology

Migration is achieved by simply swapping hardware – with no changes to the communication software.

Answer to the modem phase-out

With the final shutdown of traditional telephone networks, many modem solutions became unusable. The AT Modem Emulator allows continued use of existing systems by providing a modern IP communication path. Companies can retain tried-and-tested installations while benefiting from higher transmission speeds, improved reliability, and contemporary encryption capabilities.

Box-to-box – serial connection via IP

The box-to-box function creates a transparent link between two AT Modem Emulators over Ethernet. Serial data is transmitted bidirectionally – reliably and independently of the host operating system. Automatic reconnect mechanisms ensure stable communication even during brief network interruptions.

This function replaces classic dial-up connections between two remote modems and is ideal for:

• Long-distance connections between control centers
• Remote maintenance of machinery
• Alarm forwarding over IP

On request, the connection can be secured with TLS to protect data from unauthorized access.

Virtual modem ports for Windows

Using Windows COM port redirection, applications can continue to access a virtual COM port representing the modem emulator. The familiar modem interface remains, while the physical connection is made via Ethernet. This function is fully AT command-compatible and supports both incoming and outgoing connections.

In virtual machines such as VMware or Hyper-V, this eliminates the need to deploy complex physical COM port pass-through. Existing software remains operational without changes.

Rugged hardware and interfaces

The AT Modem Emulator includes:

• RS232 port – AT command-compatible and pin-compatible with classic modems
• Ethernet port (10/100BaseT) with autosensing and auto-MDIX

Power is supplied flexibly via PoE or externally through 12–48 V DC using screw terminals. Galvanic isolation improves noise immunity. Its housing is optimized for DIN rail mounting and complies with relevant standards:

• EN 61000-6-2 – immunity
• EN 55032:2015 + A1 Class B – emissions
• EN 61000-3-2 / EN 61000-3-3

Commissioning and management

Using the WuTility software, the device can be deployed in just three clicks. Configuration is performed via the web interface, Telnet, or through the serial port. DHCP is supported for quick integration into existing networks. Remote configuration simplifies management even over long distances.

Comparison with other modem replacement solutions

Unlike more complex IP gateway systems, the AT Modem Emulator focuses on direct component replacement. It is particularly suitable for projects where existing modem systems are to be replaced without fundamentally changing the setup.

Support for virtual COM ports and optional TLS encryption clearly differentiate it from basic RS232-to-Ethernet converters.

Typical application areas

• Climate control: remote monitoring and diagnostics of HVAC systems
• Alarm technology: secure IP-based dispatch of alarm notifications to control centers
• Measurement technology: logging and remote transmission of measurement data
• Legacy systems: integrating older modem-based devices into modern networks

Reliability and warranty

The AT Modem Emulator is designed for continuous industrial operation. Its robust design and standards-compliant construction ensure reliable performance even in challenging EMC environments. Wiesemann & Theis offers a five-year warranty, underscoring its longevity and build quality.

Future-proof migration from modem to IP communication

The AT Modem Emulator from Wiesemann & Theis is the ideal solution for replacing obsolete analog and ISDN modems with fast, secure, and versatile Ethernet communication. With virtual COM ports, box-to-box connections, and TLS encryption, it enables simple migration without altering existing IT architecture.

It provides planners, engineers, and network specialists with a cost-efficient, future-ready means of keeping proven systems operational beyond the shutdown of legacy telephone networks.