There are two categories of overvoltage protection devices: clamping and foldback, or crowbar devices. Clamping devices such as SESDs (Silicon ESD protection), and PESDs (Polymer ESD protection) allow voltages up to their designed clamping levels to pass through to the load during operation. These devices also allow for temporary voltage spikes that occur during normal use, and will not affect continuous operation. If an overvoltage event occurs, as shown on the slide with the red arrows, the device clamps the voltage at a value higher than normal, but still within acceptable limits for continued operation. This provides a steady voltage supply to the load.