Signal Surge Protection Device

A signal surge protection device (signal SPD) is installed on data and communication cables to block transient overvoltages caused by lightning strikes, electromagnetic interference, or switching events from reaching sensitive electronic equipment. Unlike power SPDs which protect AC or DC supply lines, signal surge protective device are designed specifically for low-voltage data interfaces — including RS485, Ethernet, PoE, and RF coaxial lines — where even a small transient can corrupt data or destroy interface circuits.

Signal SPDs should be installed at the point where a cable transitions from an exposed outdoor environment to an indoor or protected zone — typically at the building entry point or at the equipment itself. For CCTV systems, install one SPD at the camera end and one at the recorder end of each cable run. For RS485 networks, install SPDs at the field device and at the control panel terminal. For antenna feeders, install the RF surge protector as close to the building entry point as possible, with a short earth bonding conductor to the building’s main earthing terminal.

Each type protects a different interface. RS485 SPDs protect two-wire differential data buses used in industrial automation, Modbus, and SCADA systems — operating at signal levels of 8V to 110V DC. PoE surge protectors protect RJ45 Ethernet cables carrying both data (10/100/1000Mbps) and DC power (48V PoE/PoE+) to IP cameras, access points, and phones. RF coaxial surge protectors protect high-frequency antenna feeders operating from DC up to several GHz, maintaining 50Ω or 75Ω impedance while blocking surge currents. Choose based on the interface your equipment uses.

No, when correctly selected. Thor’s RS485 signal SPDs are transparent to data rates up to 10Mbps with no measurable effect on signal integrity. Our Ethernet PoE surge protectors support 10/100/1000Mbps (Gigabit) speeds and are PoE+ compatible. RF coaxial protectors introduce insertion loss of ≤ 0.3dB — negligible for most antenna systems. Always verify that the SPD’s frequency range or data rate specification exceeds your system’s requirements before installation

Signal surge protective devices are tested and classified under IEC 61643-21, which covers surge protective devices for telecommunication and signalling networks. This is separate from IEC 61643-11 (AC/DC power SPDs) and IEC 61643-31 (PV systems). Thor’s signal SPD range is CE certified and compliant with IEC 61643-21 requirements for the relevant interface categories.

For RS485 industrial bus protection, Thor recommends the TRSS-485 series. Available in 7mm, 14mm, and 18mm DIN-rail widths to suit your cabinet density. Select the Uc voltage matching your RS485 system level — 8V, 15V, 30V, or 110V. All TRSS-485 units provide Imax 10kA protection and are transparent to Modbus RTU communications. Contact our technical team with your system voltage and data rate for a confirmed recommendation.

Yes. Thor’s TRSS-RJ45 series is available in 4-port, 8-port, 16-port, and 24-port rack-mount configurations, with both standard plastic and EMI-shielding aluminum housing options. All units support Gigabit Ethernet (1000Mbps) and PoE/PoE+ power delivery. The 24-port aluminum model is particularly suited for IDF cabinets and data centre access layer switches in buildings with lightning exposure.

Yes. Thor offers OEM manufacturing for signal surge protectors, including custom enclosure labelling, connector types, and packaging. We work with security system integrators, network infrastructure suppliers, and electrical distributors. Please contact our team with your interface type, required volume, and branding requirements for a quotation.