2G and PSTN Replacement for Remote Monitoring

What Happens to Remote Monitoring When 2G and PSTN Shut Down?

Many remote monitoring systems for critical infrastructure still rely on 2G or dial-up modems connected to a remote terminal unit (RTU) over a simple RS-232 serial cable. When a mobile operator retires 2G circuit-switched data, or a copper PSTN line is decommissioned, these devices can lose their connectivity overnight.

Generic LTE modems are not drop-in replacements, because legacy applications expect the exact AT-command behavior of the original modem. Replacing thousands of dispersed field devices is rarely practical, especially when the service is shut down with little warning.

How SecFlow-1p Replaces Legacy 2G and PSTN Modems

The RAD SecFlow-1p IoT gateway runs a modem-emulation application in a container, configured with a profile that mirrors the original modem’s AT commands and responses. The legacy device connects over serial as before, while its SMS and data calls travel as encrypted IP data over cellular (LTE/5G) or wired networks. The field equipment and the monitoring application behind it stay untouched.

SecFlow-1p IoT gateways are deployed at more than 1,000 generator sites of a critical emergency communications network, where the existing RTUs and monitoring application run unchanged after the 2G shutdown.

This solution brief explains how SecFlow-1p modem emulation works and walks through a field deployment, including its traffic model.