Cordless Microphones

[ddouglass]

To clarify what George said about the same frequency on a multichannel reciever. What you are setting with the "channel" is a base frequency. The unit determines the frequency separation (usually about 10KHz for short range things like microphones) between microphones. The channel setting is really to prevent you getting outside interference or interfering with an outside device.
As far as licensing it is about the same as CB radio. It was ruled in court that the government could not charge for those licenses either.
According to the FCC you need a license unless they operate in the following ranges 49MHz (VHF mics), AM-FM broadcast (FM mics), 902-928 MHz (UHF mics) or 2.4 GHz (UHF mics) band.