---
title: 'Call monitoring, whisper and barge for call centres'
description: >-
  Live call monitoring software for your call center: supervisors listen in,
  whisper coaching the customer can't hear, or barge in from a browser or phone.
summary: >-
  Put a team lead on a live agent call to listen, whisper to the agent or barge
  in, and switch modes in one API call. KES 0.50/min from a browser or SIP
  phone.
date: 2026-09-30T00:00:00.000Z
type: use-case
---


## Summary

Coach an agent while the call is still going, without the customer knowing you are there. With Sautikit call supervision, a team lead joins a live call between a customer and one of your agents and picks how involved to be:

- **Listen** (silent monitoring): hear both sides. Nobody hears the supervisor.
- **Whisper**: talk to the agent only. The customer hears nothing.
- **Barge**: join the conversation. The agent and the customer both hear the supervisor.

The supervisor moves between the three at any point without hanging up or redialling, so the same line serves silent QA, live coaching and escalation.

Supervisors join from wherever they already work: a browser tab in your own app, a desk phone or softphone on a SIP account, or their mobile number.

**What it costs:** a team lead monitoring from a browser for two hours a day costs about KES 60 a day, at KES 0.50 a minute.

## Who this is for

- **Call-centre team leads** who want to coach new agents on real calls, not only in role play.
- **Quality assurance teams** who monitor live calls against a script or a compliance checklist.
- **BPOs and outsourced support teams** whose clients ask to listen in on their own campaigns.
- **Collections and sales teams** where a supervisor steps in to close a payment plan or an escalation.
- **Product teams building contact-centre software** who need live call monitoring, whisper and barge as a feature of their own product.

## How live call monitoring works in your call center

Supervision is part of the Sautikit Voice API, so it works on the calls your agents already take on Sautikit numbers, whether they answer in a browser (including Sautikit Desk), on a SIP phone or in a mobile app. You start and switch supervision through the API, from your own software.

### 1. Put a supervisor on the call

Your server names the call and the supervisor. The supervisor's browser, SIP phone or mobile rings, and they are on the call when they answer.

```js
import { SautikitClient } from "@sautikit/node";

const sautikit = new SautikitClient({ apiKey: process.env.SAUTIKIT_API_KEY });

await sautikit.calls.supervise(callId, {
  mode: "listen",
  supervisor: { type: "client", identity: "mary" }, // or { type: "phone", number: "+2547..." }
  label: "Mary Wanjiku",
});
```

In a browser app you build, `@sautikit/webrtc` answers the supervisor's leg automatically, so a **Listen** button in your own interface puts the team lead on the call a moment later.

### 2. Switch modes as the call unfolds

```js
// Once the supervisor has answered (the call.supervision.started webhook):
await sautikit.calls.setSupervisionMode(callId, "whisper"); // coach the agent
await sautikit.calls.setSupervisionMode(callId, "barge");   // join the conversation
await sautikit.calls.stopSupervision(callId);                // leave quietly
```

Modes change only through the API. A supervisor pressing keys on their phone cannot switch into barge by accident.

### 3. Let the agent know, or don't

You decide whether anyone knows a supervisor has joined. Play a tone to the agent, to the agent and the customer, or to nobody. Agents on `@sautikit/webrtc` can also see a banner such as "Mary Wanjiku is listening", driven by a `supervision` event in their browser.

Every step is also a webhook, from `call.supervision.started` to `call.supervision.ended` with the billable seconds, so supervision time lands in your own QA dashboards and reports.

## Modes

| Mode | Supervisor hears | Agent hears supervisor | Customer hears supervisor |
|---|---|---|---|
| Listen | both sides | no | no |
| Whisper | both sides | yes | no |
| Barge | both sides | yes | yes |

**Recording.** Supervision never starts a recording of its own. On a recorded call, whatever the customer heard is in the recording: barge audio is kept, listen and whisper are not. The join tone is never recorded.

**Rules.** One supervisor per call. The supervisor does not follow a transfer: a transfer ends the supervision, and you can start a new one on the call. AI-agent calls, conference rooms and callers still waiting in a queue cannot be supervised.

## Pricing

A supervisor is billed like any call leg, from the moment they answer until they leave:

- **KES 0.50 a minute**, metered per second, when the supervisor joins from a browser or a SIP phone.
- **Your normal outbound call rate** when Sautikit rings the supervisor's phone number.

A supervisor who does not answer costs nothing. See [/pricing](/pricing) for every rate.

## FAQ

### What is call barging?

Call barging is when a supervisor joins a live call so that both the agent and the customer can hear them, usually to take over a difficult conversation. On Sautikit it is the `barge` mode, and a supervisor can move into it from listen or whisper without redialling.

### What is call whisper?

Call whisper lets a supervisor talk to the agent during a live call while the customer hears nothing. It is how team leads coach agents in the moment, for example with the answer to a question or a nudge towards the next step.

### Does the customer know they are being monitored?

Only if you choose to tell them. The join tone can go to nobody, to the agent only, or to the agent and the customer. Follow the call-recording and monitoring notices that apply to your business.

### Can a supervisor monitor calls from a mobile phone?

Yes. Name the supervisor by phone number and Sautikit rings their mobile. That leg is billed at your normal outbound rate. From a browser or a SIP phone it is KES 0.50 a minute.

## Next steps

- [Supervise live calls](/developers/guides/supervise-live-calls): the developer guide, from the first API call to the agent banner.
- [Run a call center on Sautikit](/use-cases/call-center): queues, agents and outbound dialling.
- [Call recording](/use-cases/call-recording): record calls for QA alongside live monitoring.
- [Browser calling with WebRTC](/use-cases/browser-calling-webrtc): put agents and supervisors in the browser.