Certain wireless microphones have operated in frequencies that are needed for public safety. When these microphones were first designed, the frequencies they used were in between the frequencies that television stations used to broadcast television programs. With the completion of the digital television (DTV) transition on June 12, 2009, television stations no longer use the frequencies between 698 and 806 MHz (the 700 MHz Band) for broadcast. These frequencies are now being used by public safety entities (such as police, fire and emergency services) and by commercial providers of wireless services (such as wireless broadband services).

The wireless microphones that had been operating in the old TV broadcast channels can cause harmful interference to these public safety and wireless consumer services. Therefore, all users of wireless microphones (or certain low power auxiliary stations) that operate on any of the frequencies in the 700 MHz Band – including both licensed users (under Part 74) and unlicensed users – have to stop operating in this band.

The FCC is only prohibiting the use of wireless microphones that operate in the 700 MHz Band. You may continue to use wireless microphones that operate on other broadcast frequencies. Microphones with cords are not affected by the FCC’s decision. (Provided by the FCC)

More can be found on the FCC website.  I know a few manufacturers are offering a trade-in discount to buy new gear.