I agree with the majority of your statement, but I would personally shy away from a specific "Monitored by company" sign, because I try to avoid advertising my security procedures. "Oh, they use Y instead of X? Guess I'll need to bring that other device, instead." I suppose a home owner could be really tricky, and just buy the sign for Y, but have a security system for X?

Oh! On a technical note, I was watching a TV show recently (Better Call Saul...?) where someone broke into a persons house undetected. When the home owner found the person and asked how they got in so easily, the person stated that they "Cut the phone line", and that was apparently all it took. Know if there's any truth to that?

Yes, there is some truth to it. Many older systems communicate with the central station over an ordinary telephone line. More modern systems will use either a cellular communications link or VOIP.

But, the real truth here is that most criminals are pretty unsophisticated and won't even bother cutting phone lines or other cables. Most break-ins also happen through the front door, so, although it sounds great (and it is actually pretty great) to have contact sensors on every window and blanket the whole place with motion detectors, it's not really necessary. If anything, you only really need sensors on the first floor, because in spite of how the movies sometimes depict these sophisticated, cat burgler types, it's mostly just thugs who bash in or take a crowbar to your front door. That's also why advertising exactly what company your security system is from isn't a big deal: they don't care. They see "security system" and just move on to the next house.

Interesting! I hadn't considered that. :)

Not in this house. The alarm system has a cell connection. By the time you find it, the alarm signal will have already been transmitted.

Would a cell jammer stop it?

"Protected by Glock"

My favorite: "There's nothing in here worth dying for."

"Free firearms inside"?

Sounds like a bad idea either way, the trespasser might return the favor.

Is your claim that there is a class of people who invade homes while carrying a firearm, but will only use it if the other person also has one?

Yes, assuming "use" means pull the trigger while aiming at a person. If you get threatened by a gun then you'll be more likely to shoot. Do you find that unlikely to be true?

I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.

You're evading the question. When you ask me to explain my reasoning I would normally expect you to do the same. Or just say you don't care enough to properly reply, that's also fine by me. Now you spin it back to me by implying I am some sort of idiot instead, which is not very nice.