Interruptible Fold Back, AKA IFB
Interruptible Fold Back, or IFB, is a type of simplex intercom for sending a program feed and interrupt (cue) audio on IFB lines for a talent to monitor. The IFB line is comprised of three elements: Program Audio, Interrupt (Cue) Audio, and a Dip or Mute control. IFB typically uses an earpiece, an external headphone box (to permit the talent to control the audio foldback level), a program source and a control station.
How an IFB Works
An all-inclusive approach to cue talent, outside of a digital matrix system, would be to use an independent analog IFB system. These systems require what is sometimes called an IFB Control Access Unit to allow a user or multiple users in control positions (the director or producer) to select one of many IFB channels to talk to different talent. Anyone in receive positions (on-air talent, floor managers, studio, audience, talent, or remote crew) listen using talent electronics or talent stations via headphones, headsets, earphones, and/or loudspeakers. These talent user stations are often wireless in-the-ear units or wired units. In the middle, the central electronics unit provides all the necessary inputs and outputs, processing, switching, and power distribution.
Monitor loudspeakers in control areas can be connected to the IFB system such that they are muted or dimmed when the IFB is active. This will prevent acoustic leakage of control room monitor audio into the IFB during an interrupt.
Applications
Cueing talent during a voice-over commentary either on or off camera in a live or taped production. IFB is used to cue on-camera announcers and is used between studio director, on-scene reporters, and the in-studio anchor in broadcast television. Similarly, sports broadcasting uses many channels of IFB to cue announcers in various locations on the field and in booths. Live performances on stage or within House of Worship allow musicians to hear direct cures from the conductor or producer, as well as the individual music mix designated for them.