I exactly build this detector as shown in the picture and it simply doesn't work ! Why is this mod so complicated ? I've tried other methods to get this working and noticed that it only worked on very short distance even if I increased the R-range drastically.
Why not building a simple mod that simply can trigger a speaker after a range is set ? Or please post a new picture with a configuration that really works ? I need an alarm for moving enemies like biters and spitters that has a trigger range similar to the range of the artillery. An alarm that triggers only at such short distances is simply worthless.

Don't think there's upper limit on range here, auto-targetting range of artillery is 224 tiles, so guess you can set that via R=224 signal.
If you want thing to trigger a speaker unconditionally, connect it directly to a speaker - just alarm, speaker, one wire, set R, trigger on R>0.
That image shows more complicated configuration (as is written there) which is not "simply trigger a speaker after a range is set" (+ enemies are within range).

But more generally, this mod adds a circuit network element, is in circuit network category, and guess you just don't want to deal with circuit networks.
If latter is the case, I'd suggest to simply avoid and not bother with mods which are tagged "Circuit network", as they require red/green wires and basic understanding of how these work in my experience, and mostly intended for general-purpose automation of anything through these, same as this mod.

It's definitely possible to make a less complicated self-contained alarm speaker mod, and yeah, might be nice for a common use-case of alarms here, but this mod just doesn't have that atm, sorry.
And it'd probably be best to have such dedicated thing not in a circuit network category, as it'd have nothing to do with it, i.e. not a part of this mod anyway.

thanks for answering, but I tried all your proposals already before your answer without success: I placed several different combinations+radar near a nest where all types of enemies are present and nothing worked. Even if I increased the range value drastically all combinations are triggering, but only at very short range, so I suspect something could be wrong with the triggering range ?? It seems that increasing the range value has no influence on the triggering range.

I'm not against using circuit networks and I already have worked with that successfully. But it should work at the end.
The easiest way would be that you please publish more example images, there is only that one I tried without success. Thanks.

Here's a video that I quickly captured (28M, headphones-level volume): https://e.var.nz/biter-detector-demo.nz4a8etw0eeve.mp4
Supposed to show what you need to get a simple signal working, and how to adjust distance on the thing via R signal.

Note that I set R=60 as a "should be long enough" there, not 35 or 40, as with dx=31 dy=37, actual distance will be square-root(31^2 + 37^2), which is a bit hard to calculate in my head on the fly, but you get the idea. Should work the same no matter what distance you set on it.

Well, and for completeness sake - as probably also noted in the README - you can send that R signal via wire, can test range via T signal on these alarm towers, and it should enable/disable sending whatever signals are set there (including same R, if it's there).

Sorry-it's too late now, I've uninstalled your mod and installed radar-signals instead, because radar-signals has the right range and delivers number of enemies easily for processing with circuit network. With that building early warning alarms is easy and quick.
...remember: That biters are unforgivable and therefore I needed a quick and reliable solution.

No worries, glad you found the fix.