A rackmount I/O signal protector assembly for protecting telecommunications related equipment and other associated sensitive electrical components from transient voltage and current surges includes a housing enclosure, a printed circuit board disposed within the housing enclosure, and a surge protector network mounted on the printed circuit board and interconnected between an unprotected side and a protected side. The surge protector network includes gigabit surge protector circuitry formed of a plurality of voltage suppressor devices, current-limiting devices, diodes, and clamping devices. Input side connector devices are coupled to the unprotected side for connecting to incoming telecommunication lines. Output side connector devices are coupled to the protected side for connecting to customers' electrical equipment to be protected.