ANSI/ESD STM5.1 was the standard of the ESD Association that defined the component level human body model test, and it was for many years the reference used by semiconductor manufacturers in North America for classifying the sensitivity of an integrated circuit to electrostatic discharge. The method represents the discharge that occurs when a charged person touches the pins of a device during handling, assembly or test, and it expresses the sensitivity as the voltage at which the device begins to fail, from which the familiar classification levels are derived. The document specified the equivalent circuit of the human body, the resulting current waveform with its characteristic rise time, the number of discharges to each pin combination and the criteria by which a failure is judged, including the parametric shifts that count as a failure even when the device continues to function. It has since been withdrawn and replaced by the joint standard published with the semiconductor industry association.