Signal SPD (Surge Protective Device) protects high-frequency data signals. Its primary function is to minimize interference with signal transmission quality while providing surge protection. Traditional parameters such as residual voltage (Up) and surge current capacity (In/Iimp) ensure the "survival" of the equipment, while the parameters mentioned above ensure the "communication" of the system.

Insertion loss: This measures the attenuation of signal strength caused by the SPD (Surge Protection Device). Excessive insertion loss can lead to a decrease in signal amplitude, an increase in bit error rate, and a reduction in communication distance.

Return Loss: This measures the impedance matching between the SPD (Surge Protection Device) and the transmission line. Impedance mismatch can cause signal reflection, leading to data jitter and distortion, which is fatal for high-speed digital signals.

Bandwidth: The frequency range over which the SPD (Surge Protection Device) can operate effectively. The bandwidth must cover the fundamental frequency of the signal and its harmonics; otherwise, the high-frequency components of the signal will be filtered out, leading to waveform distortion.

Therefore, the strict specifications of these parameters in the standard ensure that the SPD is no longer simply a "lightning current discharge device," but a sophisticated "signal integrity guardian," whose design requires the integration of high-frequency circuits, transmission line theory, and electromagnetic compatibility techniques.