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# setTransmissionMode(_:channelUUID:completionHandler:)

Sets the audio transmission mode for the channel you specify.

```
func setTransmissionMode(_ transmissionMode: PTTransmissionMode, channelUUID: UUID, completionHandler: (@Sendable ((any Error)?) -> Void)? = nil)
```

## Parameters

`transmissionMode`

The transmission mode.

`channelUUID`

The channel identifier the participant becomes active in.

`completionHandler`

The completion handler that contains an optional error.

- `error`: An error, if any, that indicates the reason why the system couldn’t set the transmission mode.

## Discussion

> Important:
> You can call this method from synchronous code using a completion handler, as shown on this page, or you can call it as an asynchronous method that has the following declaration:
> 
> ```swift
> func setTransmissionMode(_ transmissionMode: PTTransmissionMode, channelUUID: UUID) async throws
> ```
> 
> For information about concurrency and asynchronous code in Swift, see <doc://com.apple.documentation/documentation/Swift/calling-objective-c-apis-asynchronously>.

By default, a channel’s transmission mode is [`PTTransmissionMode.halfDuplex`](/documentation/PushToTalk/PTTransmissionMode/halfDuplex) — indicating that only one participant can send or receive audio at a time. Use [`PTTransmissionMode.fullDuplex`](/documentation/PushToTalk/PTTransmissionMode/fullDuplex) to allow a person to transmit and receive audio simultaneously.

Set the transmission mode to [`PTTransmissionMode.listenOnly`](/documentation/PushToTalk/PTTransmissionMode/listenOnly) to prevent a participant from transmitting any audio.

---

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