from the photo for lionels detector it appears it has a set of lines that suggests it can be disconnected from the fast track with sensors in place? just curious is all. so if you can cut the control box off a matter of adding longer wires then you can place it anywhere you like. and will assume you can remove the fast track pins or whatever they use and use a set of rail pins for that to your atlas track?
hope someone that has done this can help you more.
as to the other detector I suggested read it all you will find it has more custom settings and features and you can power it off if it gets annoying to you I like mine and with an external speaker with volume control is a plus yes its expensive but old saying you get what you pay for. if you or someone has a video of how the lionel detector sounds like I'd like to hear it to compare with the one I have.