Final answer:
When the REV button is down on a Neotek Elite audio mixing console, the output of the monitor fader is redirected from the monitor speakers to an alternative output, such as the multitrack return or studio sends.
Step-by-step explanation:
On the Neotek Elite, which is a professional audio mixing console, the function of the REV button is to reverse the signal path of the output from the monitor section. When the REV button is engaged, typically the output of the monitor fader no longer goes to the monitor speakers directly. Instead, it is redirected to a different output, often the multitrack return or the studio sends, depending on the specific design and configuration of the console. This feature allows the engineer to listen to the multitrack or studio feed through the main monitor speakers without having to re-patch cables manually.