> For the complete documentation index, see [llms.txt](https://docs.mixeffect.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mixeffect.app/configure/switcher-pages/panels-and-buttons/select-bus.md).

# Select Bus

Change the Fill Source for the selected transition, downstream keyer, or upstream keyer. When modifying the sources for the upstream keyers, only the currently selected keyer will be active.

<figure><img src="/files/Ovo1KWEWtxf0udnhs8Ad" alt=""><figcaption></figcaption></figure>