Grade 3 contacts in the uk use two reeds, one is the open close of the door. The other is to detect masking in this way.
"The Most Secure Door Contacts Available" Claims Magnaspehere
Magnasphere says they are "the most secure door contacts available", claiming that typical door contacts can be defeated with only a cheap magnet, an "EXPLOITABLE operational flaw and construction weakness."
Magnasphere claims their proprietary design eliminates these flaws and makes high security available to any alarm system.
In this note, we take a look at the problem, Magnasphere's claims and product line, and 3 key disadvantages.
Deployed them on a government project and they worked very well. Customer felt the added security was worth the additional cost, which was a minuscule part of the entire system cost.
In many systems, I mount door contacts on the side jambs especially when using wireless sensors, so I wouldn't be using this contact as much. And the person trying to defeat the door contact would have a few obstacles to overcome such as not knowing whether the second magnet was actually holding the switch closed. Then trying to secure the second magnet to the structure might be difficult. I've not heard of many intruders carrying magnets, a compass and tape for the purpose of defeating a contact. But well prepared burglars may use these techniques.
In my own home, I have the traditional magnet contacts, backed up by exterior and interior motion detection, glass break detectors and sensors on closet doors. So, I don't feel insecure with the traditional magnetic contacts. And, I always push for added detection zones.
I suppose, if someone is worried about this type of defeat, they can install additional magnets in doors and window channels as decoys and let the burglar wonder.
In many commercial projects, particularly at warehouses where high-value merchandise is stored, I have seen many attempts to defeat alarm devices in preparation for a later burglary. This has included the removal of surface mounted magnets from the door and taping them to the contact switch, the opening of a junction box and twisting of the wires to closed-loop contact switches together, and the covering of a motion detector with tape or by placing a box on top of it. In almost every case, these acts appeared to have been committed by an insider - an employee or contractor who had daytime access to the facility.
As a result, I now specify high-security contacts such as the Magnasphere on most projects of this type, as well as make sure that alarm devices and all associated wiring are protected against tampering.
(It's amazing how few installers (maybe 25% at best) use the tamper switches provided on detection devices or provide tamper switches on junction boxes that contain connections - but I'll save that rant for another day....)
NOTICE: This comment has been moved to its own discussion: Why Don't Installers Use Tamper Switches?
I think the default thought is that these incidents are always outsiders. I've seen contacts taped together or with a magnet sandwiched in, as well. I've seen a PIR taken off the wall and just sitting on a shelf, too. Insiders can do as much or more damage as intruders.
It's amazing how few installers (maybe 25% at best) use the tamper switches provided on detection devices or provide tamper switches on junction boxes that contain connections
I agree! And I think 25% is generous. I moved that point to another thread here... so the day for your rant is today!
Out of interest in the US is there a grading standard for the installation of Alarms? So low risk grade 1, home / small business grade 2, grade 3 commercial grade 4 banks? And the same for signalling systems? Just interested really :)
Kind of, but not really.
We have UL listings for High Security Levels 1 and 2, but that only specifies requirements devices must meet, not what a given facility needs. And they're really only used for government projects. And not even all of them, at that.
To my knowledge, there's no true overarching standards for what's required for various levels of security overall.
Does the same defeat principal hold true for the more expensive "balanced contacts" that are required on most government installations?
We have been installing Magnasphere contacts on all new installations and repairs the cost is slightly more for a better device in my opinion. We also use the wireless contacts which I feel are of better quality that some manufacturers brand. These products are also made in the USA for those of us who prefer to buy American made.
We have used Magnasphere contacts with success. In addition, as many others noted, we use tamper switches. A bit of an upgraded cost, but worth it for many of our customers.
In a some cases, we use a combination of an LBM strike and door contact which provides status of both doors and locks. Seeing this more and more in healthcare facilities.
Magnasphere contacts may be installed in any orientation. The magnetic ball is attracted to the ferrous metal ring and held in place when the door is open. When the door is closed, the stronger magnetic field pulls the ball into place and closes (or opens) the circuit).
In short, Magnasphere contacts may be installed in the header or in the locking side frame.
VP - Security Products