Surges and voltage transients are a major cause of expensive electronic equipment failure and business disruption. Damage may result in the loss of capital outlays, such as computers and communications equipment, as well as consequential loss of revenue and profits due to unscheduled system down time. The TDS130 Series of surge suppressors is designed to provide economical and reliable protection from voltage transients on power distribution systems. The TDS130 is specifically designed for the protection of 1-phase power supplies within instrumentation and control applications. They are conveniently packaged for easy installation on 35 mm DIN rail within control panels. Transient discriminating (TD) technology helps ensure reliable and continued operation during sustained and abnormal over voltage events. Internal thermal disconnect devices help ensure controlled behavior at end of life. A visual indicator flag provides user feedback in the event of such operation. The TDS130 provides a set of optional voltage-free contacts for remote signaling that maintenance is required. The convenient plug-in module and separate base design facilitates replacement of a failed surge module without needing to undo installation wiring.