Clamping voltage, also referred to as let through voltage or the Voltage Protection Rating (VPR), is the amount of voltage a surge protector permits to pass through it to the attached load (ex: a TV) during a surge event. Clamping voltage is a performance measurement of a surge protector’s ability to attenuate a surge, or more simply, to reduce the surge to a manageable level. For example, a surge protector might limit a 6,000V surge so that only 600V is ‘visible’ to the load. The clamping voltage is 600V. This performance value is confirmed by Underwriters Laboratories during tests conducted while evaluating a surge protector for listing.