Should be one in every tech toolbox
This fits into the "why didn't I think of that?" category. I worked at a company that had two of them and after working a freelance job without a QBox that had signal issues, I immediately bought one for myself. Listen to signal at almost any point in signal flow of any system, while sending signal at the same time. Plus you can use it as a listen box or down and dirty communication! Every tech should have one in their toolbox. Great build quality, size and overall design.