PTX-3 on September 29, 2015 | Marketing Team Wireless IFB (interruptible fold back) systems are used for talent cueing and crew communications in broadcast and motion picture production. In other cases, the IFB system is used by directors and other management to monitor program audio during a production. UHF wireless IFB Transmitter basestation with 256 selectable frequencies at 100kHz increments. Stand alone or rack mountable with the PRK-2 kit. (614.400 - 691.100 MHz). Non-RoHs NOTE: This product is not approved for sale in Europe.