Talk to one panelist. The room hears nothing.

ZComms is a talkback and IFB station for productions that run on Zoom. The panel is a grid of keys, and a key wears a person's name — hold it and your voice lands in that person's ear alone, while the meeting floor, the recording, and everyone else carry on unaware. It rides the Zoom Meeting SDK's own talkback channels: no virtual audio cable, no second machine, no bot account.

Download for Windows How it works View source

A named key per personEvery talkback-capable participant gets a standing channel of their own, and the key wears their name. ALL CALL spans the panel; latch makes a press stick.

Private, not disruptiveTalkback is its own path, so nothing you say reaches the meeting floor. Members duck under your voice while you are keyed and return to unity when you let go — ducked, not muted.

Extern feedsLatch one channel — or a stereo pair — of a multichannel interface into a talkback channel, so a larger intercom, a console bus, or a Dante feed uses Zoom as its last mile.

Honest keysA key reads live only while someone is actually hearing you. Keyed into an empty channel reads amber; a person in another breakout room reads dark, names the room, and refuses the press.

How a key reaches one ear

Zoom's Meeting SDK carries a talkback path alongside the meeting floor: up to 16 channels, each holding up to 10 people, addressed independently of the room. ZComms provisions the whole bank once when it joins and then assigns people to it — keying selects a channel, it never tears one down and rebuilds it. Your voice goes down the channel you keyed and nowhere else; the meeting mic stays open, because Zoom requires an open mic to deliver talkback at all, but it is fed nothing, so the room stays silent. That is a pure SDK arrangement — no audio driver is installed and no loopback device is created.

Members of the channel you key are ducked rather than muted: their meeting audio drops under your voice and comes back to unity the moment you release, so talent never loses the room. The duck is gated on the signal actually present, not on the state of the key — a latched extern feed that happens to be silent leaves the room at full level.

What is on the panel

Keys and the grid

One cell per talkback-capable participant, carrying their Zoom name
Hold to talk, latch to stick, and LATCH ALL for a standing open line
ALL CALL across every provisioned channel in one press
Numbered slots for direct keys, reassignable from the panel

Channels and privacy

16 talkback channels, up to 10 listeners each, provisioned in one pass
Channel isolation verified live — a listener on one channel hears nothing from another
Members ducked while you key and returned to unity on release
The meeting mic held open but fed nothing, and re-asserted as housekeeping

Extern feeds

Any channel or stereo pair of a multichannel interface, latched into a channel
Per-feed gain and limiter, downmixed to mono because SDK sends are mono-only
Input meter reading −60 to 0 dBFS across 12 segments, pre-envelope and post-gain
The −50 dBFS signal gate drawn on the scale, so "present" and "counts as signal" are distinguishable
Feeds persist across launches

Capture chain

Input gain, look-ahead limiter, then a ramped PTT envelope — edges ramp, they do not gate
Echo cancellation referenced against ZComms' own monitor output, defeatable
Sidetone tapped after the envelope, so it monitors what is actually being sent
Device pickers that switch live, plus a built-in test tone

Breakout rooms

Zoom talkback cannot cross breakout rooms — the panel says so rather than failing quietly
Cells for people in another room go dark, name the room, and refuse the press
The station can move itself between rooms from Settings
Chat used as a signalling side-channel for cues and notifications

Joining and control

Sign in with Zoom once through the browser (PKCE) — every join happens as your account
Paste any meeting link or ID; no bot account and nothing for panelists to install
The panel is served on 127.0.0.1:7350 with an SSE state stream
A one-line action API on the same port — the seam a Stream Deck or Companion module drives

What it needs

Windows 10 or Windows 11 (x64). The installer is per-user and needs no administrator rights; the Zoom Meeting SDK ships inside it. There is no macOS build yet.
A Zoom account you can sign in with. ZComms joins as you, through the same OAuth broker CoreVideo uses. There are no anonymous joins.
Panelists on a native Zoom client, desktop or mobile, with nothing installed on their side. The Zoom web client cannot receive talkback at all — the panel labels those people rather than pretending the key works.
A headset on the operator position is still best practice, echo cancellation notwithstanding.

Early software, honestly

ZComms is at v0.1.14 and is early. Talkback delivery, channel isolation, the duck behaviour, and breakout awareness have all been verified in real meetings. Extern feeds have not yet been proven in a live meeting — they are covered by unit tests and bench-verified against real hardware, but the in-meeting gates are still open. Expect rough edges, and please report them on the issue tracker.

The build is not code-signed, so Windows SmartScreen warns the first time you run the installer — "More info", then "Run anyway". Signing is waiting on a developer account, not on a decision.

Download ZComms for Windows Source & release notes

Where it fits

ZComms and CoreVideo are separate products that came out of the same problem — running a real show inside somebody else's Zoom meeting — and they share the Zoom Meeting SDK and the same sign-in broker. ZComms is the standalone desk: it is what you run when the intercom is the job, on its own machine or beside a switcher that has nothing to do with Zoom.

The CoreVideo plugin is growing an intercom dock of its own so an operator already cutting a show in OBS can key talent without leaving it — that work is on main and has not shipped in a release yet. ZComms is the answer when talkback wants its own operator, its own position, or a feed from a bigger comms system, and it is the only one of the two you can download today.

Product	Form factor	Talkback
ZComms	Standalone Windows app	The whole product — a full desk, extern feeds, and its own operator position. Shipping now.
CoreVideo for OBS	OBS Studio plugin	An intercom dock beside the video routing, for the operator already cutting the show. In development, unreleased.