First, enter a Daily domain and room name. You can use my defaults, but you might make some new friends:

Optional, but recommended: Press this button to open that room in Daily Prebuilt in a new tab (so you can see the effects of what you're doing).

Open Prebuilt in a new tab

Click the "Load cameras" button to see all of your available camera devices:

Load Cameras

Next, select the camera device you want to use:

Then, click these buttons to start or stop the camera. If you stop the camera during the call, the camera's light will turn off.

Start Camera Stop Camera Start Screen Stop Screen

Finally, join the room:

Join Room

You can change the "enabled" property of the camera track using these buttons. Disabling a camera track makes its video unavailable to your app, but it doesn't turn the camera off. This means the camera's light stays on, and re-enabling the track is much faster, since you don't have to wait for the camera to restart.

Enable Camera Track Disable Camera Track Update Send Settings

Take a look at the setupVideo() function in the page's source code to see how to handle various MediaStreamTrack events from the camera. To leave the room, close the tab or refresh the page to start over.

To learn more, check out the source code of this page on Glitch.