Wireless IFB (interruptible fold back) systems operate between 486.4MHz and 639.9MHz. They are used for one-directional communication. Directors and other management can use this to monitor program audio or for talent cueing and crew communications during a production.
NOTE: This product is not approved for sale in Europe.
NEW FCC REGULATIONS:
Going forward, anyone selling a wireless microphone or other device designed to operate in the restricted 600 MHz wireless service band (617-652 MHz / 663-698 MHz) will be required to notify buyers at the point of sale that the device may no longer be used after July 13, 2020, and that users may be required to cease operation earlier if using the device could cause harmful interference that disrupts wireless communications for new service licensees. DA 17-709
The manufacture, import, sale, lease, offer for sale or lease, or shipment of wireless microphones or similar devices intended for use in the United States that operate on the 600 MHz service band frequencies (617-652 MHz and 663-698 MHz) is prohibited after October 13, 2018 ( See FCC 15-100, FCC 15-99, DA 17-314, FCC 17-95).
https://www.fcc.gov/wireless/bureau-divisions/mobility-division/wireless-microphones