This is supposed to be a communications business. We build visual and audio communications with our viewers. Everything behind the scenes is done to get the artistic vision of a producer on the screen. And to do that we have to communicate with each other. Timely communication today consists of Twitter, e-mail and texting, but in a production environment, we rely on voice communications.
The evolution of intercoms
Early productions adopted the same communication system in use for consumers: effectively telephone operator headsets. Using carbon granules, which change resistance depending on pressure on a flexible membrane, a microphone was simple and effective. Earpieces were equally simple and demonstrably uncomfortable. When I Googled “carbon headset,” I got bicycle parts first, showing my age mostly. But for many years, good communication that worked in noisy environments was elusive.
Then, in about 1973, Clear-Com introduced remote headset amplifiers that could clip onto a belt. Multiple beltpacks could be chained together and shared a remote power supply. By 1975, RTS was in the game with similar products, including multichannel systems, all remotely powered. Using an audio hybrid, high-quality and less susceptibility to feedback was achieved in these products. Over the next few years, the range of portable and permanently mounted desk and rackmount user stations were developed by both companies. Within a few years, having an intercom in your production truck became a necessity for entertainment shows.
The simple beltpack grew over time to be a family of communications products, initially entirely based in analog audio. By using mix-minus techniques, it was possible to put many users on a common channel and enable them to be heard superbly.
The single-channel beltpack in the early 1970s systems evolved into the multichannel systems of today. Three-, six-, 12- and even 24-channel systems have become common. For example, lighting can have its own channel, but the lighting director can bridge on more than one channel to keep in close communication with the rest of the production staff, including video and the director, relaying messages to his operators without putting multiple operators on one channel. Replay producers or assistant directors may have direct communication with each operator while maintaining partyline capability for speed and urgency. Video operators can isolate their communication with a cameraman without interfering with critical production communication.
A camera operator may speak privately with a dolly operator while still hearing everything the director is saying. In a news production, the technical director might speak privately to an engineer checking in remote feeds, or a graphics room might communicate with the producer about the graphics needed for a live production. Master control might monitor all of the producer's and director's communication to anticipate when breaks will roll, but may not want the rest of the production chatter to fill the channel. A full matrix system allows these listen-only open mic circuits to be set up efficiently for each use.
A peek inside intercoms
Beginning in analog, and now available mostly as digital systems, these complicated communications systems matrices work on four-wire approaches, where sending and listening are done by connecting output and input to separate busses in a matrix approach, summing all parties speaking to each output individually. When two-wire stations, such as beltpacks, are connected, an audio hybrid (or active two-four wire converter) is used to extract the separated talk and listen signals. (See Figure 1 on page 36.) The technique works in a manner similar to mix minus in an audio console from a user's standpoint, with some side tone from a user's microphone added back into the listen signal fed to the earpiece of the headset.
In matrix systems, each user can be assigned, or choose from their user interface, every source they will hear and to which other users they will speak. For example, a buss might be set up for all operators to share like a partyline, but the director can separately and privately speak to any member of the crew he desires on a selectable basis. Individually, levels both talk and listen, for each crosspoint connection can usually be established in software from a GUI or perhaps from the user's own station.
The programming software is often capable of storing and recalling multiple setups. This makes setting up for a program that happens regularly simple. It can allow a person's name to be assigned to a channel, simplifying and personalizing the labeling on the panels. By crafting and storing a master setup and then making incremental changes to customize the setup for each program, one can make complicated setups more understandable. As in all things, there are trade-offs with some system programming software. Each vendor's capabilities are subtly different, and it is wise to ensure that reprogramming a single panel does not take the entire system offline. Even if it is for a few moments, it can make small changes difficult to schedule when reprogramming for an upcoming production while even a portion of the system is in use.
As might be expected, the range of options creates its own set of issues, principally the growing complexity of the user interface needed to make access to the multiple features available. The RTS801 Master Station of the late 1970s and early 1980s had a hidden panel with a row of listen levels associated with each buss. While that was effective, it required someone who was not technically challenged, and more than one producer had his hands slapped by a tech manager who asked him to stop creating problems. Digital technology has provided some isolation between finger gepoken and the underlying software control of the matrix driving a user's panel. Often today, panels have programmable legends on switches allowing each program to have its own detailed setup with the names of the personnel called out clearly on the panels.
As the sophistication of intercoms grew, it became possible to add direct communication to talent headsets using IFB (interrupted feedback). IFB user stations can't communicate bidirectionally like other user stations, but can be connected to a buss with program audio or a mix-minus feed, with the ability of producers, directors or others to interrupt the sound to speak directly to them. Common in news and sports broadcasts, IFB is a minimum price of entry for live production today. I have often used IFB channels to allow stations overseas to communicate with talent doing live news shots thousands of miles away by connecting a remote IFB output to the local program audio input, but preserving the ability of local technicians to speak directly to the talent during lineup of the remote shot.
It is, however, often useful to consider simple systems, for example in an ENG van. A simple two-wire, beltpack-based system might suffice where cost and complexity are issues. Most camera CCUs allow connection to an external intercom, often four-wire. Crafted carefully, a system might have a two-wire interface for the technician in the truck and four-wire to the camera. By using a small matrix system, IFB and connections to the studio are often simplified. Though more expensive than a simple two-wire system, a small matrix can offer benefits worth considering. But if the budget will not allow even a small matrix, this can also be accomplished by using a four-two wire converter and VoIP carried over the digital ENG microwave between the studio and the remote. This allows the remote to be fully integrated into the studio environment, even enabling remote mix minus for IFB to be integrated tightly between the control room and remote.
Digital matrices often provide other features, which — while not applicable to small installations — provide capabilities critical to large installations and particularly ones spread out over large local or remote campuses. Multiple matrix frames can often be connected together to create much larger virtual systems. In a large production center, each studio might have a matrix of its own that is interconnected to a master frame where all operationally separate units can be combined to facilitate large productions needing more facilities. A newsroom in New York and another in Washington can work on the same production and communicate as if they are just down the hall. This might be built out using VoIP channelized technology, or a dedicated high-speed link that connects the busses in related products together. VoIP can also allow connection to a private branch exchange (PBX) system for bringing remote personnel in the field into the production, or feeding IFB to remote talent. All systems also allow dial tone lines to be connected using telephone hybrid options.
IP influences
Modern intercom user interfaces allow many useful options developed for IP-based industries. Some current matrix systems offer color LCD display options, which hold the promise of rich user interfaces with clear and understandable displays of critical user information about available connections. As new developments in IT technology become available, intercom systems will adopt every innovation that enhances deployed communications systems. For example, we might see interface text-based systems popping up on communications panels with a beep indicating “you have mail,” allowing messages with less sensitivity to be aggregated onto a fewer number of user interfaces.
Such messaging enhancements would be simple to integrate in IP-based systems, perhaps even showing up as script notes in a cameraman's viewfinder. Merging cutting-edge communication and networking tools into production communication could help make the latest generation of production personnel comfortable with our time tested verbal communications systems.
John Luff is a broadcast technology consultant.
