Rallying to the Defense of the Reed Switch

Magnetic reed contacts are not only the first line of defense in an alarm application, but also the least expensive and most reliable product for a building’s perimeter. Recently another technology that uses a metal can and a little ball was featured in SSI‘s March issue (”A Breakthrough in Alarm Switches”). The article discussed the advantages of a particular sensor device while tearing into present reed-switch based technology.

Don’t get me wrong, I like the company’s technology featured in the article when it comes to special biasing of contacts. However, there are facts that should be known about today’s reed contacts before spending two to three times more money on something so simple.

Reed switches today are generally made of rhodium or ruthenium encased in glass and sealed in nitrogen. Tane’s reeds are so reliable that when we founded our company in 1985 we offered a $50-1 lifetime guarantee for any defect that required a service call. It is significant that reed switches have the advantage of sitting unused in back doors for years and then working that one odd time when called upon.

These same reeds can also go through one hundred million operations without a hitch. Because reed switches are made of glass it is no myth they can be fragile. A magnetic contact will most likely fail if an installer hits it with a hammer when applying it to a recessed application. If a technician is using a hammer to install a contact, can you imagine what other bonehead things he is doing on the job?

Reed switches are considered so reliable that they are a critical component on smart airbags and anti-lock brake (ABS) applications. What’s more, it was Tane’s switches used in the NASA rovers that so triumphantly explored the Mars landscape. Think of the G force the switches endured when the rovers made that famous bounce landing!

It Ain’t Broke, So Don’t Fix It

The article in SSI’s March issue said the standard magnetic contact can be defeated with another magnet. Let’s use a little common sense here, please. If you have a contact recessed in today’s door, how are you going to slip another magnet next to it to defeat it without opening the door? Also, if you slip another magnet near it you have only a 50-percent chance of actually defeating it, even if you can find the contact at all.

If defeating contacts for standard installations was an issue in the burglar alarm business, do you think this product would still be around after 40 years? In fairness, I do like the other technology for what would be called a “high security” application. These applications are more expensive and can justify the extra fees these contacts cost.

In that same article, a comment was made on contacts breaking during shipping due to improper handling. In surveying our shipping records of hundreds of thousands of reeds and magnetic contacts per month, we find less than a .001 percent ever come back broken. Yes, a box of contacts will smash if run over by a road flattener. Otherwise, they will survive the sloppiest shipping company dropping and tossing boxes. All contacts start with an outer housing of plastic or metal. We use hot melt on most of the products to protect the reed during shipping, as well as on swelling of doors so the contact does not crush. Some companies use epoxy to accomplish the same results.

To be sure, reed contacts and other alarm parts are susceptible to the rare instance of a lightning strike. A lightning strike may fuse the contacts depending on where and how it hit the home. If it is a direct hit, the contacts can be fused but then so may the panel.

Years ago the makers of the old Moose Products panel made a magnificent reed contact that when hit by lightning fused open. The problem with the switch was that no one wanted to spend more money for something that happens so infrequently. The same can be said for the technology using the little ball. We have found in our surveys that in this competitive world, people do not to want spend more than they have to for something so simple and reliable as the magnetic reed contact.

Tab Hauser is President of New Hyde Park, N.Y.-based Tane Alarm Products, a contact manufacturer. He can be reached at [email protected] or (800) 852-5050.


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