This standard sets terms@ test methods@ test circuits@ measurement procedures and preferred result values for the surge parameters of isolating transformers used in networking devices and equipment three types of isolating transformer are considered; mains low frequency power@ high frequency power (switching mode power supplies) and signal (eg Ethernet data) the surge parameters of the isolating transformer insulation barrier covered by this standard are: - Rated impulse voltage - Input winding to output winding capacitance - insulation resistance Additional parameters for signal isolating transformers are: - Core saturation voltage-time product Purpose The main purpose of this standard is to define a series of transformer impulse withstand voltage ratings that are higher than those of IEEE Std 802.3TM [B6]1with the intent to improve transformer insulation performance in uncontrolled environments. In the interests of international standardization the voltage values used are harmonized with the series defined in IEC 60664-1 [B7] for low-voltage equipment insulation coordination. This IEEE standard is applicable to home networking insulations@ which are typically uncontrolled environments@ where the surge voltage levels and corresponding required transformer impulse withstand voltages can be higher than the LAN A controlled environment as defined by IEEE Std 802.3TM [B6]