Whilst UPSs guard against over and under voltages, surge boards are limited to only guarding against over voltages, specifically spikes and surges. A good surge protector will quickly clamp, not allowing the spike to reach your equipment, keeping it safe. Most surge boards are self-sacrificing meaning that they will fail to work after absorbing a surge. This is a good thing as PowerShield surge boards retail for way under the $100 mark but can protect equipment that is much more expensive. Some surge boards come with a Connected Equipment warranty which guarantees your equipment if it is connected to the PowerShield surge board.
