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What Are IFB, Comteks And Camera Hops?

Plus, Taking A Look At The Zoom F4 Mixer/Recorder
Lectrosonics IFB T4 transmitter
Lectrosonics provides some of the most popular wireless systems.

Communication on a set is a big deal. If you haven’t worked in larger productions, you should know the most common audio concern besides miking and recording talent for the production is on-set communication.

In my experience, this type of communication can be divided into two main categories, plus a third smaller category, which is mainly used for documentary-types of productions and reality shows.

1. Communications From The Director, AD And Producer

The first is communication from the director, AD and producer to the crew. Although the days of directors wielding megaphones are a bit past their prime, directors and especially assistant directors still need to have on-point communication with their crews.

IFB, or interruptible foldback (IFB), is also known as interruptible feedback, interrupted fold back or interrupt for broadcast. In essence, it’s a monitoring-and-cueing system used in television, filmmaking and video production for one-way communication from the director or assistant director to on-air talent or a remote location. The IFB is a special intercom circuit that consists of a program feed sent to an earpiece worn by talent via a wire, telephone or radio receiver that can be interrupted and replaced by the director’s or assistant director’s intercom microphone.

2. Live Audio Program Monitoring

Second, key members of the crew also need to be able to hear dialog from the talent as they act out the scenes. The director, ADs, producers, writers and script supervisor, as well as other key members of the crew, need to hear dialogue.

Comtek receiver
Comtek receivers are in use on many TV and movie sets all over the world.

Comtek, which has become synonymous with live-audio program monitoring in production, makes mini-base station transmitters, like the BST 75-216, as well as rack-mounted base-station transmitters, like the BST 25-216 and the PR-216 receivers. The Comtek transmitters also work with other manufacturer receivers as well, but in my experience, Comtek has a large market share in the television and film-production markets.

Comtek BST 75-216
One of the most popular single-channel Comtek transmitters.

3. Camera Hops

There’s a third type of on-set communication—often found in certain types of productions such as reality shows and documentaries—that’s different than the first two. It refers to how to transport sync sound being recorded to the cameras themselves. While the audio recorded on the sound mixer’s outboard recorder is often the audio used in the end product, film crews also find it helpful to have a summed mix of all channels being recorded and have that mix duplicated on the audio channels of the cameras.

Here are a couple of reasons why this third type of communication can be helpful: It allows for easier casual viewing dailies. The crew can also perform rough-cut edits with the camera audio (often referred to as scratch tracks) without having to locate, sync and output audio from the sound mixer.

Generally, in higher-end productions, sound is recorded on the sound mixer’s recorder/mixers, most typically on models like those from Sound Devices or Zaxcom. But there are other brands used, as well.


Sound is delivered to post and synced with the picture. The camera and sound recorder are tied together with identical time code, and often a smart slate that displays the time code is slated and photographed at the head or tail of each take. Often, no sound is recorded on the camera because it simply isn’t needed in this type of workflow.

In mid- to lower-end productions, like multi-camera reality television or event productions, the editor and producer/director prefer a summed audio feed from the sound mixer to also be recorded on at least some if not all of the cameras. In the past, the sound mixer was often hard-wired to the cameras, with a line output recorded onto each camera. This allows for quick review of the previously recorded scene with sync audio in place.

Often on these types of productions, as many as 10 or even 20 channels of wireless microphones and boom mics are recorded, each to its own discreet channel on the sound mixer’s recorder. But the sound mixer often outputs a two-channel summed mix of all of this audio, which is run into the cameras.


As I noted previously, a camera hop is a wireless audio system used to transport the summed mix to each camera. Here’s how it works: A wireless transmitter is attached to the sound mixer’s output, and wireless receivers are used on each camera to receive a two-channel output from the mixer.

A camera hop can utilize almost any quality wireless microphone system, but the most commonly used systems are UHF wireless systems made by Lectrosonics, Micron and Zaxcom.

Often these systems aren’t the same quality and expense level as the wireless systems used to mike the talent and receive the signal on the sound mixer’s end since the camera-hop sound is mostly used as a scratch track for syncing or just simple viewing of the video.


But understanding these systems is key to comprehending all of the communication necessary in a production environment. Keep in mind, these systems are also typically joined by wireless radios (walkie-talkies), as well, making a typical production set a hotbed of wireless communications.

Zoom F4 Multitrack Field Recorder

Zoom F4
The Zoom F4 is small but is a full-featured, sophisticated audio recorder/mixer that’s laid out for bag or cart use.

A few years back, we reviewed Zoom’s F8 Multitrack Recorder. And while Zoom had been better known for lower-end sound recorders, like the H4N handheld recorder, the introduction of the F8 as a recorder intended for a more professional audience was an interesting development. In fact, the F8 recorder set a new bar for the number of features included in a sub-$1,000 recorder/mixer. It’s why it was a big hit.

Not long after, the company followed up by introducing the Zoom F4, which cost even less than the F8. Recently, I had a chance to use the F4 on two different projects to determine if it’s a still a viable option for recording on a budget.

Pro-Audio Features On A Budget

The Zoom F4, which you can buy for under $500, is a six-input, eight-track field recorder. It has four Neutrik Combo series mic/line sockets on the left-side panel that record to tracks one to four. Two more inputs can be fed from either a 10-pin connector on the rear for recording to tracks five and six or via the 3.5mm TRS “Camera Return” socket on the right side panel for monitoring.

Zoom F4 Four Neutrik Combo
Four Neutrik Combo plugs can accept line- or mic-level inputs, providing phantom power.

The stereo mix can also be routed to three different stereo outputs: The Main output on a pair of 3-pin male XLRs, the Sub output on a 3.5mm TRS socket and the headphone output on a 6.5mm TRS socket. An internal mixer allows a stereo mix to be recorded to tracks seven and eight.


All four preamps are the same as the ones used in the F8. Each input is individually switchable to phantom power. There’s optional MS decoding, the ability to link multiple trims (gain controls) together and a PFL button that offers a choice of PFL or Solo monitoring.

The F4 In Use

The first project I used the F4 on was an audio recording for a documentary that was shot at a press event. At this shoot, I was able to try the F4’s mic preamps with a Schoeps CMC641 Super cardioid microphone and an Electro-Voice RE-50N/D-B handheld dynamic microphone. The resulting recording sounded warm, intimate and clean. I was also impressed with the clarity and transparency of the F4’s preamps.

The display on the F4, in comparison to the F8, is smaller and not as refined. But all in all, it’s usable. I was set up at a small Da-Lite Projection table with the mics set up just a few feet away.

Zoom F4 outputs
The Zoom F4 provides a variety of output options.

For this project, we recorded a dozen interviews over two days, and the F4 performed perfectly. I was very impressed at the quality and features. But because this was an audio-only recording, I didn’t have a chance to try the F4’s time-code capabilities. Still, overall, I liked the fact that we were recording to two separate SD cards. It generally makes me paranoid to only record on a single card at a time with any device. SD cards aren’t as robust as CF or CFast 2.0 cards, in my mind, and I’ve had several cards go bad over the years.


The F4 In A Sound Production Scenario

The second scenario was a two-camera documentary shoot of three subjects seated in a semi-circle. One camera was on a tripod with a long lens to grab singles and doubles. The second camera was mounted on a Rhino EVO Pro Motion Control System grabbing a wide, slow-moving shot.

We decided to use the F4 as an out-time code-master source, feeding the BNC time-code output from the F4 to the time-code input to the A camera. We then looped the time-code output from the A camera to the B camera’s time-code input. We also fed the F4’s XLR outputs to the XLR inputs of the A camera.

We did not run-loop the audio to the B camera as the XLR audio cables provided too much weight and drag for the motion control slider. Our thinking was that the F4 audio and the two cameras would share an identical time code. So, just having scratch audio on the A camera would suffice.

Zoom F4 memory card slots
The Zoom F4 provides dual-card recording for backups and security.

The shoot went smoothly. Just like on the first project, the sound was clean, clear and impressive for such a low-cost device. The time-code output was rock solid, and both the cameras and the F4 audio matched perfectly in post.


The Zoom offers flexible options when it comes to recording: You can record all your inputs and your mix on one card. Or you can record in duplicate with a full backup running on your second card. You can also distribute the ISO recordings and the mix across the cards. I put the ISOs (inputs one to six) on one card and the mix on card two.

Bottom Line

Overall, the F4 really impressed me, and sometimes I’m still amazed that a sub-$500 recorder has so many options and features that work so well.

Of course, it’s not a Sound Devices or Zaxcom recorder, but it costs a fraction of the direct competition from those companies. Additionally, the new Sound Devices MixPre recorders are excellent, but the F4 offers a lot more features at a price that’s even lower than the MixPre-3.


In my view, the F4 offers a lot of value for the price. At the very least, it’s well worth a listen. It’s perfect for users who aren’t full-time professional sound mixers but still need a full package of pro-audio features at an impressively low price with solid quality.

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