The simplex-type has two communication stations cabled to each other with a push-to-talk (PTT) switch; some may be voice-activated. Users may send and receive, but not at the same time.
When you need to get rid of push-to-talk switches, you want full duplex. It's more complicated, with transceivers programmed to transmit on one frequency and receive on another, allowing both (or all) persons to talk at the same time. It's sometimes called party-line technology for that very reason.
Digital matrix intercoms are multi-channel, multi-functional communications systems, and are fully programmable so that any simplex or duplex communi-cations can be sent and received by all. Digital matrix systems also let users control audio levels, giving each person a unique mix.
In any case, users communicate via gooseneck micro-phones connected to a headset or headphones, all driven from belt-worn packs or rackmount components. Some intercom rigs are compatible with a variety of headphones to further customize the system, depending on the type of production. Be aware that headphones come in different types, too: circumaural, in which a small speaker is enclosed in a padded device that blocks out most or all other sounds; intraural (like a hearing aid, the listening device fits inside the ear canal itself); and supraural, in which the speaker sits outside the ear.
Circumaural headphones can be either single- or dual-muff; this catchy phrase refers to the covering of one or both ears.
Whichever you choose, know that choice of headgear can be just as crucial as choice of intercom technology. If the headset isn't hygienic, comfortable, and convenient to use over long stretches of shooting time, or if the sound itself is not clear, a video crew may be less inclined to use an intercom properly.
So comfort, configuration, and even the ability to easily wash the earphone covers are important considerations when you are selecting headset components at this level.
MAX headsets from Riedel are designed for noisy locations like Formula One race tracks. Nevertheless, they are comfortable and light, with soft detachable headset cushions. The rotatable gooseneck allows the microphone to be on either your left or right ear.
Production Intercom single-muff headsets are very lightweight (about seven ounces) yet come with a flexible steel reinforced boom mike. And the comfortable ear cushions are machine-washable.
Beyerdynamic DT 297 headsets are extremely comfortable padded headphones, featuring full frequency sound and speech reproduction (10Hz-30,000Hz) for clear, crisp communication in any shooting situation.
There also are several connection standards for intercom headsets; they may or may not be universally compatible. Clear-Com, Telex, and RTS each have their own, for example, but adaptors or other interface devices are available.
A WORD ON WIRES
Another issue to consider is wired versus wireless. Many event videographers would normally not think twice about such a choice—wireless is so much more convenient (especially during set-up and strike).
But wireless intercoms (like wireless anything) pose hurdles on location that you will want to overcome long before the actual production day. Generally, they operate on VHF or UHF frequencies, and may be susceptible to interference (not to mention FCC licensing requirements, depending on operating power and frequency) in many places.
Wired systems bring their own considerations. Cables, shielding, and connections must be solid and robust to survive heavy usage. Capacitance (resistance to signal strength and high frequency response) can be an issue in systems with total cable length—not just the longest single run—of 500 feet or more.
One of the least expensive and still functional intercoms available is the Nady PRC-3X/DM wireless unit. For $139, you get a single or double muff adjustable headset that's part of a full duplex (VHF) system. The unit also features a call or page mode if the receiver is not being worn, a low-battery LED, and removable steel-spring belt clip.
A very efficient and economical choice of many event videographers is the TD 902 system from Eartec. It's a wireless, full duplex system configured for two, with prices starting at $300.