Which organization has standardized the configuration of receptacle contacts?

The National Electrical Manufacturers Association (NEMA) is the organization that has standardized the configuration of receptacle contacts. NEMA focuses specifically on electrical equipment and components used in the U.S. and has established standards related to the design, configuration, and performance of electrical receptacles, plugs, and connectors. These standards ensure compatibility, safety, and reliability when connecting electrical devices to power sources.

Organizations such as ANSI, IEC, and IEEE may also play significant roles in various electrical and electronic standardization efforts, but NEMA's specific focus on receptacle contacts and configurations distinguishes it as the correct answer in this context.