EOL resistor question

Well I guess aside from the fact that surface mounted contacts tell the whole world exactly how your alarm works from a glance across the room, the only difference would be that surface mounted contacts can be disabled by virtually any tradesman possessing minimal knowledge, less than 60 seconds of time, and the tools/supplies they normally carry. Also after they disable the contact only a close inspection would reveal the tampering.

For example:
painter: break off razor blade after cutting into wire
cable guy: wrap fine filaments of cable wire shielding between contacts/temrinal screws
phone guy: wrap single strand of stripped cat3 between contacts/terminal screws
plumber: piece of solder wrapped between contacts/terminal screws
carpenter: nail/screw into wire

I'm still trying to think of the trade that normally carries a suitable magnet.

In short, disabling surface mounted contacts is a simple crime of opportunity whereas disabling recessed magnets requires pre-meditated intent as well as an opportunity to closely inspect the window.

Gatchel, look into Nascom's switches. In between their BMS' and recessed contacts, it'll supplement most requirements for security and not be the large "safe" contacts of old. Magnaspheres still aren't commonly stocked items for most trade distributors, but they're out there. We've been using them for about 4-5 years now. It still won't address a person getting to the wiring and compromising that, but getting units with integral EOLR's is the option. If you have people that have the time and abilities to access wiring to compromise it, you've got larger issues to address.

@ Lou, reread my post, I put the suggestions out there before others provided the handy links. If someone's going through the efforts you've listed, it's not a crime of opportunity and nothing is going to stop them.They can pull a recessed contact and do the exact same things you're listing as caveats for surface contacts just as easy and just as fast in doing such.For that matter, I might as well just fire up a welder on your property and create some EMP to take care of the system...just as quick and easy. In the scenarios that you listed, a properly installed EOLR (or even though I'm not a fan, EOLR's inside the contact) would detect the defeat methods you started detailling (to a point), but the argument is still going to be academic.

If the concern is wiring, and access to such, then wiring routing methods should be implemented to avoid the scenarios you noted...there's no reason a cable would be exposed if the install is performed properly, nor would screw terminals or other compromise points exist.

A standard recessed or surface mounted reed switch can easily be compromised with a strong enough defeat magnet. Hell, most trades and even standard people carry a rare earth magnet of some sort. My newest torpedo level has ones that'll overpower most magnets that come with the contacts. Magnetic pickup tools are another one. It's not even like it needs to be a "standard" magnet...just look for the closest speaker.

Not going on a tangent, but speaking from experience and dealing with high risk sites, assets and places subject to repeated compromise attempts, many times I've installed multiple switches and detection circuits, hell, even dummy contacts for the specific purpose of creating the "tamper" event. As I said, if security is paramount, a single, normally closed detection circuit with a single closed contact being installed is not going to be how it's done.
 
@Dell

points

1) It really is much simpler to load a screw in a screw gun that you are legitimately using in someone's home and walk over to a window and in less than 5 seconds drive a screw into an exposed wire and unlock the latch. Opening the window, popping the contact, shorting it then putting it back in and closing the window takes much longer and a home owner who walks in on this activity will be immediately alarmed to something amiss. The person would be caught red-handed and lose their job and get reported to the police if I was the home owner and walked in on that.
2) Setting off an EM bomb in my front yard seems unlikely. Anyone with that skill level and the confidence that their em bomb is actually powerful enough to have for sure fried my system has bigger fish to fry. Then consider that they probably just fried much of the stuff that they might have wanted to steal and I stop worrying about that.
3) While it can be easy to use a magnet to defeat a standard reed contact, in practice it is a bit more challenging. Considering that in my personal installation the windows and the window frames and the location of the reeds in the frames prevents a person outside the house from getting a magnet closer than one inch from the reed. It requires a very strong magnet to work at that distance. I did test the situation and could not get it to close the magnet reliably even with a powerful shop magnet. In the perfect position I could get it to work about 50% of the time, but the slightest jiggle and it failed. Consider that with the alarm on and the window closed, one would not know if they had actually succeeded until they opened the window, and then any movement of the magnet while prying the window open and it fails. I am certain a juiced up electromagnet would do the trick, but again, specialized tools generally are only found in the hands of criminals with bigger targets than my house.

Here is the final conclusion. It is measurably more challenging to defeat a recessed, in-the-frame contact and it is otherwise a pretty equal installation. That and the aesthetic advantage leads me to consider it the superior route (unless your windows can't accommodate it).

Putting redundant systems in high risk areas is a fine idea. I think it is a great approach particularly in commercial sites where you have employees with access to the door/window frames. Using one more obvious contact would give a would-be criminal the false sense of thinking the system was defeated when it was not because of a second hidden contact. I definitely endorse that approach. In fact, the very first alarm I ever installed 20 years ago was sold to me by a family friend who owned a security company. He did that very thing to his offices and actually caught one of his employees who falsely thought he had defeated the security system but was unaware of the second contact. The employee really thought he was going to get his security system boss but found out the hard way he was not as skilled as he thought.
 
Lou,

If you install a system with supervision, the issues with a damaged wire start to lessen...to quote what you said elsewhere, it's all statistics. Now, your EOLR system and how it's implemented is going to come into play. More secure systems do not use single EOLR and NC loops, so a shorted wire is going to be detected the instant it happens. In the case of a residential system, how it's installed is going to be the key, and while NC loops are more common, there's plenty of ways to make them more secure. I also believe you are viewing surface contact installation methods as they're installed on a "Florida" style window because of your location in the US, where the sash itself tends to sit outside the window bay,with either sheetrock or other materials being used as a "return" to trim out the window, necessitating exposed cabling.

The same nefarious persons that are going to drive a screw or short out the wiring are just as adept at driving screws into recessed contacts or crushing the reeds, shorting out the cabling without even pulling the contact out.

Specialized equipment or hardware is not needed to defeat standard magnetic contacts, recessed or surface. It's the nature of the beast. EMP is easily produced by any welder, so it's not going to be an "EMP bomb" and if it's localized to a circuit location, the damage is not going to be widespread. I've had to fix systems damaged in such a manner, so I've seen it firsthand. A good rare earth magnet is all you need, not a juiced up electromagnet or large horseshoe or similar.

What I'm saying isn't conjecture, I've installed and serviced many sites with high risk of tamper or compromise...institutional and residential, I've seen plenty of contacts compromised or attempted to be compromised. If the magnet can get put close enough, there's plenty of ways to get it to stay in place while the compromise attempt is being made. As I stated, if security is paramount, there's design criteria for a system that start getting thrown out of consideration.

If what you've tested on your own system using methods you feel are within the realm of probability for your site, more power to you, rock on, but I disagree with your statement saying that your recessed contact is inherently more secure....the only difference between the two is whether or not one is visible or not and how it's mounted.

There's a reason why many of the higher security contacts don't have screw terminals,, or if they do, there's only a single reference marking that's wiped off after installation. They have NO and NC loops, in addition to magnetic tamper and pry tamper connections....even all the wire leads coming off them are the same color, with only a temporary dyechem marking and stickers, both intended to be removed after installation, and end up with 8-10 conductors being connected and they don't work unless the magnet is spaced properly, not simply in proximity, so you're sitting with a meter while hooking them up.
 
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