GearCast - Intercoms for Stage and Production Buyers Guide

Humans are hard-wired with a need to communicate. The history of long-distance communication harks back to ram’s hornDefinition:
A very efficient form of loudspeaker that couples well to the air, typically with an exponential flare. trumpets, smoke signals and semaphore telegraph using arms and flags. Mechanical annunciators (levers, strings, bells and flags) and voice pipes (speaking tubes) in 18th century ships and buildings preceded the invention of the telephone in the 19th century.

The telephone allowed people in different parts of a building to communicate and this became common in theaters in the earlier 20th century. The invention of the vacuum tubeDefinition:
(slang) A vacuum tube or (valve), an electronic amplifying or rectifying element with a heating filament, in a glass or metal envelope. in 1912 then allowed amplifiers to provide paging to dressing rooms... but we’ve come a long way since then.

Prior to the 1960s, conventional telephone operator headsets were used for communication in theater and television.

Until recently, most studio video cameras were standardized for compatibility with carbon microphoneDefinition:
Vibrates a capsule with granules of carbon, which varies the resistance of a DC current to make electrical waves. telephone headsets. However, traditional telephone operator-style headsets were not very loud or could reject ambientDefinition:
1.  Something in a close vicinity. 2.  The natural sound of a space, or simulation of being in that space. noise. In theater, it was important that backstageDefinition:
An area not open to the public where preparations for a performance take place, typically located behind the stage. people speak quietly to each other; a better solution was needed. Then in the late 1960s, loud rock music shows became the norm, and the operators of sophisticated lighting and sound equipment had to communicate with each other in noisy environments. Conventional telephone headsets were useless for that application.

Birth of Clear-Com and Distributed Amplifier Intercoms

In San Francisco, Bob Cohen was producing rock shows (at the Family Dog and Avalon Ballroom) and worked with Charles “Charlie” Butten to invent the first intercomDefinition:
A device that provides voice communications between two or more points. In entertainment, allows communications among stage/studio personnel, and for video, handles director to camera communications. system that worked in a high-noise environment. It involved designing a distributed amplifierDefinition:
1.  A device that increases the voltage or power of a signal. 2.  In music performance, a device such as a guitar amplifier that includes speakers and controls to increase the sound level of acoustic or electric instruments. belt-pack system. In 1968, Clear-Com was incorporated to manufacture the new system. Since then, all stage and production intercom systems have descended from that design.

Types of Intercoms

Intercom means Inter-Communicator and technically anything that allows two or more people to talk—residential door entry systems, educational and industrial communications, or communications between people in or on a vehicle—is an intercom. This buyer’s guide focuses on intercoms used in theater, performance and video production applications, although the technology is equally suitable for other applications (like inter-factory communications).

Hard-Wired Intercoms

Hard-wired professional intercom systems require cables between stations and usually a power supplyDefinition:
A device (internal or external to another device) that provides power for active circuitry. Can be AC, DC or battery-powered. or main station. The most common cables are standard XLR microphone cables and RJ45Definition:
Also called 8P8C connector. An 8-conductor connector for Cat5/6 cabling for Ethernet, Dante, and HDBaseT and other video-over-twisted pair extenders. CAT5/6 EthernetDefinition:
A local area network (LAN) using cables classified according to certain categories (CAT5, CAT6, CAT5e, etc.). These relate to the speed a cable can handle. cables. The advantages of hard-wired systems are that these cables are readily available and interchangeable for other applications and the intercom lines can be routed through existing infrastructures for audio and dataDefinition:
Information used by a computer in order to arrive at a decision. Although this is a plural term, it's often treated in the singular. communications.

When Clear-Com introduced their system, they called their standard “Partyline,” meaning multiple people could talk on a shared line at the same time. Some of the newest designs use IP-Network protocols.

Wireless Intercoms

Walkie-talkie type radio communicators have been around since World-War II. The limitation with two-way radios is that they are simplexDefinition:
Communication over a single cable or radio frequency. communicators, where only one person can talk at a time; while someone is transmitting on that shared frequencyDefinition:
A value, expressed in Hertz, that indicates how many cycles of a periodic signal occur in one second. , no one else can talk or interrupt. This is why professionals say “over” to notify everyone else that they are done talking, so the next person can talk.

Being able to talk and hear simultaneously is called duplexDefinition:
Signal transmission in both directions at once. See also: Half Duplex or Simplex. communication. There are two types of wireless duplex systems. One uses a base stationDefinition:
The primary control station for an intercom system or main dispatch radio for land-mobile radio systems. to connect all the wireless portable belt packs together and interfaceDefinition:
A device that adds I/O capability to another device. Common would be a MIDI, audio or video interface for a computer. with wired systems. Some newer systems do not need a base station; the belt packs communicate with each other directly, via digitalDefinition:
A signal or data expressed as series of the digits 0 and 1, typically represented by values of a physical quantity such as voltage or magnetic polarization. spread-spectrum frequency hoppingDefinition:
Also Spread Spectrum, a radio-frequency signal that changes frequency to avoid interference..

Wireless systems deliver greater mobility than hard-wired systems, but like wireless microphones, are prone to interference and limited batteryDefinition:
An assembly of series-wired cells that provides higher voltages than individual cells. life. They also cost more. Hybrid systems that interface a wireless system with a hard-wired system are common, so that those who need mobility can use wireless, while stationary users can go through the hard-wired system.

Wireless belt packs that talk and listen (bi-directionalDefinition:
A microphone or speaker that operates in two directions simultaneously, with one side "in phase" and the other 180-degrees out of phase. Also called "figure-8." communication) are called transceivers (TRANSmitter/reCEIVERS). One-directional communication uses wireless IFBDefinition:
IFB (Interrupt For Broadcast), (Interrupt Feedback), (Interrupt Foldback): A headphone/earphone program monitor intercom feed "interrupted" by a program director to cue announce talent. (Interruptible Fold Back) receivers. This allows directors and others to monitorDefinition:
1. (audio) A loudspeaker or headphone/earphone used for accurate reference monitoring for recording or broadcast.  2. (live performance) A device that reproduces sound, like an in-ear monitor or speaker wedge, so performers can hear themselves. See: IEM.  3. (computers) A device that provides a graphic representation of operations occurring inside the computer.  4. (video) A device that enables seeing what is occurring with a video shoot, or program material from a broadcast or other video media source. audio, cueDefinition:
1. (verb) Monitoring and getting a program event ready to go, or direction to talent to commence a program or portion of a program.  2. (noun) A particular piece of music in a video, film, or TV score associated with a particular on-screen event. talent, or communicate with a crew during a production.

Note that some systems offer encryptionDefinition:
Scrambling a signal, which requires decoding to decipher. to stop eavesdropping. This is especially important in sports coaching systems, so the opposing team cannot hear plays.

Cellphones

Using cellphones is problematic, because call reliability depends on getting a good signal from a tower, which is not reliable in many buildings. This is especially true in a theater or stadium with a lot of wiring and high-powered electrical equipment. Although two people with decent headsets may be able to communicate with cellphones, communicating among multiple people requires setting up a conference call each time. This can work, but cellphones were never designed for professional show or event communication.

Intercom Features

Channels

Basic systems have everyone on the same channelDefinition:
1. In radio, television, citizen's band radio, and other wireless communications modes, a specific frequency for communication.  2. In mixers and video, an input or output signal path with controls.  3. In MIDI, one of 16 data paths.; however most systems provide multiple channels so different groups can communicate. In a theater that might be the lighting and sound crew, with the stage manager being able to talk to either or both. A video crew needs a director to talk to camera operators, without interfering with others. Most multichannel systems can be reconfigured easily to place different stations on different channels.

Interoperability

Unfortunately, most intercom system brands are not compatibleDefinition:
Capable of operating with a particular selection of hardware or software. with each other. Each system has its own way of connecting and communicating. Even different systems offered by the same manufacturer don’t necessarily have interchangeable stations. However, interfaces exist that can interconnect two different systems. This might be needed when a traveling show wants to interface their own equipment with a venue’s installed house system, or when a video crew has one system and is shooting at a venue with a different system for backstage communications.

Signaling

Some type of alert function is needed for users who may not be wearing their headsets all the time, or are using speaker stations or stations with telephone style handsets. As a result, most systems have either flashing lights (annunciators) or tones to get a user’s attention.

Contour

Because these systems need to support intelligible communications, even in high noise environments, the station electronics should have a frequency responseDefinition:
The range of frequencies that an audio, video or data device can pass. contour (shape) that emphasizes consonants and suppresses sound out of the spoken voice range (e.g., bass frequencies).

Side-Tone

Side-Tone, a standard feature on telephones, is the ability to hear oneself when speaking. Side-tone lets you know that you’re sending a signal, especially in wireless systems. The side-tone volume should be loud enough to know you’re speaking, without drowning out other people’s voices. In some systems, the level is adjustable.

Program Injection

For cueing actors in dressing rooms, system channels can be used with speaker stations. So, some systems have a line-level input into which you can inject a signal (such as a show monitor microphone). This allows the actors to hear the production’s progress and is also applicable to anyone who needs to hear the show but might be isolated in a box office, boothDefinition:
Control Room. Drum or vocal room in a studio., production truck, etc. This program feed must be controllable, so as not to drown out communications.

IFB (Interruptible Fold Back)

IFB is like to program injection as mentioned above, but has a different goal. Most intercom equipment is used backstage for technical personnel, stage management and video directors to communicate with camera operators. IFB reverses the communications flow to communicate with talent. In applications like newscasting or sportscasting, the announcers often have earphones or headsets that allow the talent to hear each other as well as remoteDefinition:
A broadcast from the field, not from the studio. A Remote Control. feeds. IFB allows a director to interrupt the liveDefinition:
Live broadcast of an event or program without substantial delay or editing. feed audio in the talent’s headset/earset to give direction—like going in or out of a station break, or informing the talent of breaking news.

Tally Lights

In multi-camera video production, tally lights indicate which camera is on the air. This light is usually visible for both the talent (to know which camera the audience is seeing through) and for the camera operator, to help avoid any sudden moves or lens adjustments. This signal to triggerDefinition:
A signal that starts an event. the tally lightDefinition:
A signal lamp on a camera or monitor that indicates it's recording, or "on air.". comes from a broadcast-quality video switcherDefinition:
A device that selects from multiple signal sources, for audio, video, or data. In broadcast video production, a combination of switching, preview, and crossfading that uses a video mixer.. In intercom systems designed for video production, the trigger feeds through the intercom’s wiring to the camera stations and then to the tally light.

Types of Stations

Power Supply

Most hardwired intercoms need a power supply. It can be a stand-alone supply with no other functionality, or built into a main station. Usually, a system only needs one power supply, but multiple supplies may be used in large installations (assuming that all power wiring is localized).

Main Stations

Main stations are common in wired systems and used in some wireless systems. These are usually AC-powered in a tabletop or rack-mount configuration, with the system power supply built-in for hard-wired systems. The main stations feature a built-in headsetDefinition:
A headphone with boom microphone for intercom, communications, learning labs, gaming, or sportscasting. station and may include a loudspeaker for monitoring. Most main stations can control two or more channels, communicate with all the channels, separate or join the channels, or even program individual out-stations. Think of the main station as the central switchboard. In theater, it’s usually located at the stage manager’s position or in the booth. In television, it’s located in the control room or mobile truck.

Rack Stations, Unpowered

For more complex hard-wired systems, multiple remote, multi-channel stations are available without the power supply, because only one power supply should be used in most systems.

Belt Packs

Belt packs are the most common form of station for both hard-wired and wireless systems. For hard-wired systems, the belt packDefinition:
A portable, body-worn device, often an intercom, wireless mic, or listening device. It gets its name because they is often a clip for making a secure attachment to a belt. is usually powered through the connecting cable. For wireless systems, belt packs are battery-powered.

The belt pack will have a headset connector, which is typically 4- or 5-pin XLR. The system connection is usually 3-Pin XLR and there may be a second connector to loop throughDefinition:
A method of daisy-chaining multiple pieces of equipment from a common source, and may require a terminator at the end. See: Daisy Chain. to a second station. You’ll likely find a signal flasher to get your attention and a button to flash others. A volume control for the headset is standard, along with a microphone muteDefinition:
1. To silence or squelch an audio signal.  2. A switch that silences a signal. switch (to reduce noise pickupDefinition:
1. Transducer attached to a musical instrument that converts mechanical vibrations into an electrical signal for recording or amplification.  2. The part of a phonograph that translates mechanical motion from grooves into electrical signals for subsequent amplification., you want to keep the mic off unless talking). There may also be screwdriver trimDefinition:
A gain control for microphone inputs. controls for microphone sensitivityDefinition:
In transducers and amplifiers, the how much input energy is needed to produce the desired output. or side-tone adjustment. Multichannel belt packs will have controls to determine which channel it’s on.

Portable Stations

This is usually in the form of a portable box—basically a belt pack, but larger and with a handle (those with a speaker are often called a “biscuit”). Some include a built-in microphone, with push-to-talk or voice (VOX) triggered talkbackDefinition:
A communication system between rooms, typically control room and studio.. They’re frequently used during rehearsal in the audience by the show director, who wouldn’t want to wear a headset.

Wall Stations

Wall stations are permanently mounted. They may be a wall-mount version of a belt pack, or a speaker station with a built-in talkback microphone, or connector for a microphone or headset.

Interfaces

Interfaces link different brands and types of communication systems. Some interfaces will link to 2-wire or 4-wire telephone-type connection, while others link to 2-way radios.

Headsets

Selecting a headset needs to take into account comfort, environment and budget. When used in a high-noise environment, a dual-muff isolating ear-cup design with a noise-cancelling microphone is critical. If the environment is quieter, a single muff, either enclosed or foam style, will be better. For portable camera operators, a single muff allows getting closer to the viewfinder eyepiece. Also, those who need to communicate acoustically with people around them need either open-foam or single-muff headsets. Headsets designed for high fidelityDefinition:
Reproduction of sound that's faithful (has fidelity) to the original sound. or gaming are a poor choice for intelligible voice communications.

It's important that the headset have the right impedanceDefinition:
Also abbreviated as Z. The resistance to AC current flow, measured in ohms (similar to, but not necessarily, the same as DC resistance). and connectors for specific intercom systems, so you can expect headsets offered by the intercom system’s manufacturer to be compatible. Other headsets may work, but some research will be needed to check for compatibility. Ruggedness and repairability are important.

Other features to look for include cable type (straight or coiled), cable length and connector. Some headsets have either a built-in belt pack, or are permanently wired to the cable. These headsets are less expensive but less serviceable, because the headset and its cable are most prone to failure. Finally, note that some headsets have a mute switch built-in on the boom micDefinition:
A highly directional mic for video/film-sound held on a pole, typically over an actor and out of the frame. swivel so that raising the mic mutes it, while lowering to the mouth un-mutes it.

Handsets and Microphones

Telephone-style handsets are available as an alternative to headsets for users who do not need to, or should not, wear a headset all the time (e.g., front-of-house sound mixers). The handsets typically have a squeeze-to-talk switch in the handle. In some applications, it’s better to use a push to talk (PTT) handheld or gooseneck microphone attached to a station. These microphones will have the same connector as a headset.

Interconnect

With hard-wired systems based on 3-Pin XLR audio wiring, connections are made in parallel and can use junction boxes for portable equipment and terminal strips for permanent and rackDefinition:
A frame for holding gear that meets an industry standard for enclosures. This specifies a 19 inch width, and a height that is some multiple of 1.75 inches. A rack frame can be open or enclosed, and has rails drilled with standardized screw holes for attaching rack equipment. wiring. CAT5/6 based IPDefinition:
1. IP (Internet Protocol): A digital data standard over Ethernet.  2. IP (Ingress Protection): A rating of an electrical device, such as a lighting fixture, regarding protection from foreign objects or water.  3. IP (Intellectual Property): Refers to creations of the mind, such as inventions; literary and artistic works; designs; and symbols, names and images used in commerce. Intellectual Property is protected in law by, for example, patents, copyright and trademarks, etc.. Network systems use standard Ethernet routers and switches.

Where to Find Help

Consult GearCast for more on information on intercom systems and feel free to call our helpful consultants at Full Compass to answer your questions. We’ve encountered all kinds of situations that require reliable communications and the correct solution can vary considerably—it all depends on the venue and specific communications needs. At Full Compass, we can recommend what will provide the best results, while making it possible to stick to your budget.