Before revision: In the United States, Part 15 of the U.S. Federal Communications Commission rules specifies that no license is needed if FM transmitters' signal strength reaches 250 µV/m measured at , which usually equates to having a Maximum Effective Radiated Power (ERP) of 0.01 microwatts.
After revision: In the United States, Part 15 of the U.S. Federal Communications Commission rules specifies that no license is needed if FM transmitters' Maximum Effective Radiated Power (ERP) of 0.01 microwatts.