Getting the crew to hear each other
Comms is the only system on a show where every department has to hear every other department, live, hands-free, and without ever getting to say "sorry, say again". That makes it the one place where latency stops being a number on an analyser and becomes something a person can feel.
The shape of it
Four ways to build a talkback system
They are not competing products so much as four different answers to "who hears whom", and most real shows use two or three of them at once with interfaces in between.
| System | Duplex | How it works | What it costs you |
|---|---|---|---|
| Partyline (2-wire) | full | One balanced pair carries DC power and audio to every beltpack on the line. Everyone hears everyone, all the time, summed together. Green-GO is the networked equivalent. | No routing at all, and noise adds with every pack. Clear-Com and RTS use different conventions and do not simply interconnect. |
| 4-wire | full | Separate send and return pairs, so a circuit is genuinely point to point rather than a shared bus. | More cable and no inherent "everyone hears everyone". It is a building block, not a system. |
| Matrix | full | A central router — an RTS ADAM or equivalent. Every panel gets its own configurable set of keys, so the stage manager hears the departments they need and nothing else. | It has to be programmed, and the programming is a design job with opinions in it. |
| Wireless beltpack | full | DECT at 1.9 GHz is the modern default — FreeSpeak II, Bolero. Older systems sit in UHF or fight for 2.4 GHz. | Antenna coverage is a survey problem, and every wireless link adds latency the wired system did not have. |
| Two-way radio | half | One channel, one person at a time, push to talk. Cheap, instantly deployable, and everybody already knows how to use one. | Half duplex, hands occupied, and no simultaneity. This is not an intercom and it does not become one. |
The thing people get wrong
A walkie-talkie is not an intercom
Radios are excellent and every show has them. They are also half duplex, and half duplex is a different kind of conversation from the one a show runs on.
Calling a sequence means speaking and listening at the same time — hearing the flyman acknowledge while you are still on the second half of the standby, hearing a "hold" cut across you the instant it needs to. On a radio you cannot hear anything while you are transmitting, so a hold arrives after you have already said "go".
The other half is your hands. A beltpack with a headset leaves both hands free and the channel permanently open. A radio takes one hand and a deliberate act, every single time.
Use radios for the things they are good at: crew spread over a site, security, load-in traffic, anything where the conversation is occasional and the geography is large. Do not run the show on one.
The number that decides how it feels
Latency, and conversational turn-taking
Human conversation is timed far more precisely than it feels. Turn-taking in ordinary speech has gaps measured in a couple of hundred milliseconds, and people begin planning their reply while the other person is still speaking. That is a reflex, and it does not adapt to a system that is late.
An analogue partyline is effectively instantaneous. A digital matrix adds a few milliseconds. Audio over a network — Dante or AES67 — adds its packet time and buffer. A wireless beltpack adds its own coding delay, and a system that goes wireless to a bridge to a network to another wireless system adds all of them together.
Once the round trip gets long enough, something specific happens: two people start a sentence at the same moment, both stop, both restart. It is not that the audio is bad. It is that the timing cue everyone relies on has been moved.
Drag the dial and watch what the same two people do to each other.
- Every interface is a latency budget you did not write down. Wireless to bridge to network to matrix to another wireless system is four delays in series, and nobody owns the total.
- Analogue partyline and digital packs on the same show do not agree about time. One is instant, the other is not, and the person hearing both hears an echo of themselves.
- VOX has no place on a live channel. Voice-activated open mics put a coughing electrician on the stage manager's call. Latching or momentary, never automatic.
- Sidetone is not a luxury. If a user cannot hear their own voice in the headset they will shout, and everybody else will turn down.
- Clear-Com and RTS partyline are not the same standard. They can be interfaced, and they cannot simply be plugged together.
The other pieces
IFB, program, and who should hear what
IFB — interruptible foldback — is the talent's ear: normally carrying programme sound or a music mix, and interruptible by a director or stage manager who needs to say something over it. It is a different job from crew comms and it is worth keeping it a different system.
Programme feed is the show itself in a corner of the crew's ear, and it is what lets a follow-spot operator or a flyman work to what they can actually hear rather than only to a call.
Listen-only positions — bars, box office, front of house staff — need to hear the call and must not be able to join it. That is a routing decision on a matrix and a hardware decision on a partyline.
The design question underneath all of it is the same: the stage manager should never have to hear a conversation that is not theirs. Every channel, key and interface exists to protect that.
Licensing
The question that surfaces when a show travels
Wired comms is a cable and nobody's business but yours. Everything wireless sits in spectrum, and spectrum is national.
Licence-exempt bands exist for radios — PMR446 in Europe, FRS in the United States, and the equivalent low-power allocations elsewhere — and they come with power limits and no protection from anybody else using them. Licensed channels cost money and give you a channel that is meant to be yours.
DECT-based intercom sits in a band reserved for it in many jurisdictions, which is a large part of why it became the default: it is not competing with the venue's Wi-Fi.
The rule for a touring show is unglamorous. Check the band before the freight leaves, not on arrival, and treat every country as a separate answer. The frequency map is the starting point for the ones this site covers.
Naming, channel conventions and who calls what differ between theatre, broadcast, arena touring and film. If your region works differently, open an issue — that variation is the sort of thing worth recording rather than flattening.
- Partyline or matrix?
- Why not just use radios?
- How much latency is too much?
Where to go next
These pages are a chain rather than a library — the next one along usually answers the question this one raised.
Everything on this page, in the index
Each of these has its own entry with sources, ports, gotchas and an open gap where a field is missing.