Protect signal lines using two-stage protection with a resistor in-between.
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At the line end, install a 10 kA capable gas discharge tube (GDT) to system
ground.
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Install a series impedance.
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Install a 600 W or 1.5 kW transient voltage suppression (TVS) diodes from line to line and from all lines to signal ground.
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For best protection, select the TVS diode voltage to be as low as the used signal permits.
Figure 1. Signal Line Protection