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Old 18 August 2009, 06:53 PM
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Cell Phone Cell phones deactivate card keys

Comment: I have heard many times that a cell phone can deactivate a hotel
room magnetic key. Is there any truth to this?
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  #2  
Old 18 August 2009, 07:07 PM
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It is if someone uses a cell phone to call the guy's wife and tell her he's in room 523 with a cute blonde.
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Old 18 August 2009, 07:09 PM
SoToasty SoToasty is offline
 
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Quote:
Originally Posted by Brad from Georgia View Post
It is if someone uses a cell phone to call the guy's wife and tell her he's in room 523 with a cute blonde.
Please, That does NOT deactivate a room key. I can deactivate the guy. Or possibly the cute blonde.
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Old 18 August 2009, 08:37 PM
Mycroft Mycroft is offline
 
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In throry it could, but principly because of the permanent magnets in the speaker (and it would not have to be operating or even switched on).
In practise the speaker magnets are small and well shielded for the reason that cell phones tend to be kept in pockets/handbags close to bank cards etc; where any magnetic field would not be welcome,
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Old 19 August 2009, 02:15 AM
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It's happened to me more than once. I didn't believe it would work before either. It's a pain in the butt too because it's easy to stick everything in the same pocket. Last year at the beach we had 3 key cards and everyone stuck them into their pockets with their cell phones. None of us could get into the room.
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Old 19 August 2009, 02:20 AM
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It's happened to me once too by storing the key in the same pocket as my phone.

Although correlation is not causation and all that...
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Old 19 August 2009, 02:24 AM
blucanary blucanary is offline
 
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Quote:
Originally Posted by Lachrymose View Post
It's happened to me once too by storing the key in the same pocket as my phone.

Although correlation is not causation and all that...
True but it's happened so many times to me now that I can't help but think there must be some link.
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Old 19 August 2009, 03:03 AM
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I stayed in a hotel for 5 days this summer as a chaperone for dance convention, and kept having problem with the keys - so did the other moms - they told us that keeping them by cell phones would mess them up. We had about 7 cards between 3 girls and I and all of them had problems even after we tried to keep them away from the phones. *shrug* I finally got one card that worked reliably and kept it away from the phone (even though that was a pain in the butt when going down to the pool with just the phone, card, and a towel as it would have been handy to fold the card up in the phone) and it seemed to continue working.
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Old 31 August 2009, 01:54 AM
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If it helps, my Blackberry Pearl has a built-in magnet near the back of the phone above the battery. The magnet has been known to pick up small paper clips, so it has noticeable strength. AFAIK, the main purpose is to react with another magnet in it's case or belt holster (also one that I've detected using small metallic objects) to place the phone in standby and lock the keyboard against accidental use.

Don't ask me why the magnet in the phone couldn't be replaced by a small metallic spring/relay that would open a suitable circuit when near the magnet in the case - I didn't design the thing!
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Old 31 August 2009, 02:23 AM
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My guess would be that since those cards are semi-disposable, that is the hotel does not care if you take them away after your stay, they are made to a much lower standard than say a credit card to keep costs down. That would include the materials in the magstrip. Any number of factors could come into play to stop it working. Friction between the card strip and other objects in your pocket might do it.

I have an embarassing TMI which I won't share, but it involved a gastric unfamiliarity with the local cuisine and a non-working cardkey which I wanted to access the bathroom in my room. A new cardkey was required - the existing one had simply died of old age and overuse.
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Old 02 September 2009, 07:47 AM
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Key cards are just really cheap, I think...though the last time I stayed in a motel, I always carried my card right next to my phone and it just kept letting me in. (It was a miserable room in a miserable motel, I kind of wish it hadn't...)

On a wildly unrelated note, my phone battery has a terrible time keeping a charge these days, but I notice it's always way worse whenever I spend more than half an hour at my friend's grandma and aunt's house an hour north of here, even if I charge it after leaving (and once I charged it overnight there, only to have the battery bars drip off the moment I unplugged it). I've noticed that my friend's aunt's phone is always beeping low battery there too. I haven't been over there in a couple of weeks now and my phone is acting much better. Is this just a coincidence going along with my phone being stupidly old by now, or is it something to do with their house? At first I thought maybe it was something to do with maintaining a signal on an hour-long highway drive, but it's definitely only when I visit them. What am I missing here that is the obvious, non-chemical explanation?
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Old 02 September 2009, 11:38 AM
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Quote:
Originally Posted by Native Medley View Post
Key cards are just really cheap, I think...though the last time I stayed in a motel, I always carried my card right next to my phone and it just kept letting me in. (It was a miserable room in a miserable motel, I kind of wish it hadn't...)

On a wildly unrelated note, my phone battery has a terrible time keeping a charge these days, but I notice it's always way worse whenever I spend more than half an hour at my friend's grandma and aunt's house an hour north of here, even if I charge it after leaving (and once I charged it overnight there, only to have the battery bars drip off the moment I unplugged it). I've noticed that my friend's aunt's phone is always beeping low battery there too. I haven't been over there in a couple of weeks now and my phone is acting much better. Is this just a coincidence going along with my phone being stupidly old by now, or is it something to do with their house? At first I thought maybe it was something to do with maintaining a signal on an hour-long highway drive, but it's definitely only when I visit them. What am I missing here that is the obvious, non-chemical explanation?
Some (possibly all newish) phones adjust their signal output to the local conditions. In a good reception area they put out less signal strength to reduce the load on the battery, in bad reception area the signal output is cranked up to max. This affects the drain on the battery. Even when you aren't making a call, the cellphone is intermittantly communicating with the network, so it can be ready if you want to make a call.

So it is possible that they either live at the edge of a cell, or there are obstacles between their house and the nearest cell tower that are causing the phone to work extra hard to find a signal.
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Old 02 September 2009, 11:11 PM
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Hm. I keep my cell, my hotel keys, and my magnetic nametag all in the same pocket in my purse and I've never had a problem.

Anecdote disclaimer, etc.
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Old 03 September 2009, 06:12 AM
Troberg Troberg is offline
 
 
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Quote:
Originally Posted by Eddylizard View Post
My guess would be that since those cards are semi-disposable, that is the hotel does not care if you take them away after your stay, they are made to a much lower standard than say a credit card to keep costs down. That would include the materials in the magstrip. Any number of factors could come into play to stop it working. Friction between the card strip and other objects in your pocket might do it.
I agree, they are usually crap quality. Here, they've even started skimping on the material, making them out of wood instead of plastic. Combine that with mechanical damage from a phone or a key ring, and they fail.

The speaker magnet is unlikely to erase it, as magnetic storage is very resilient to permanent magnets. I've tried to erase 3 1/2" disks with strong neodymium magnets, without success (I did it as a test of the safety of keeping the phone in the same pocket as the backup tapes). As far as I'm concerned, erasing disks with magnets is just a Hollywood myth.
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Old 03 September 2009, 06:56 AM
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Quote:
Originally Posted by Eddylizard View Post
So it is possible that they either live at the edge of a cell, or there are obstacles between their house and the nearest cell tower that are causing the phone to work extra hard to find a signal.
Hadn't thought about the location...it makes sense, though they're only about a street over from my friend's house where I don't have that problem at all. The line must be really weird. I always get a consistently pretty average signal.

and my phone sucks anyway.
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Old 03 September 2009, 07:26 AM
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Quote:
Originally Posted by Native Medley View Post
Hadn't thought about the location...it makes sense, though they're only about a street over from my friend's house where I don't have that problem at all. The line must be really weird. I always get a consistently pretty average signal.

and my phone sucks anyway.
Line of sight is the important thing. You can be 20 feet away from someone else and if there's a patch of old insulation or a microwave between you, you may well not get a very good signal where the other person's is fine. That's a big part of why no wireless company at least in this country can guarantee your phone will work *inside* of your house. The company I work for will even go so far as to send someone out to your area to make test calls in your vicinity to confirm things won't work (if they haven't gone out there before; the point is to find where our service really doesn't work, not to test whether people are lying or not).

What phone you're using can also make a difference. They really shouldn't - right now, every device that's out there uses pretty much the exact same radio - and yet I can point to a couple phones in our company's past lineup that do, legitimately, work in areas other phones do not. Both of the phones I can think of off-hand have these little flimsy antennas that you can extend from the device. Again, they *really* shouldn't work, but...
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Old 27 January 2016, 04:09 AM
DisneyWizard DisneyWizard is offline
 
 
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Default Coercivity and the legacy of Alexander Graham Bell

Quote:
Originally Posted by snopes View Post
Comment: I have heard many times that a cell phone can deactivate a hotel
room magnetic key. Is there any truth to this?
Coercivity and the legacy of Alexander Graham Bell

Having been primarily a computer scientist with a job as night auditor and hotel captain, my extensive first hand experience with the relationship that mobile phones have on wiping hotel mag-stripe keys is - yes mobile phones are able to completely degaus, and no, unused phones by themselves do not affect hotel access mag-stripe key cards. Human behavior is the greatest factor with that pairing.

I shall begin with a distant relative, tangentially tied to the key/mobile mythologies of the hospitality industry. Supermarket swipe is the other story, like sandpaper grinding, the POS terminals get a lot of use, and that wears away the read head, effectively widening the read gap on the head which causes more than a single polarity change to be read at once. There is no "magic property" of the plastic shopping bag, such as static, which enable a credit card to be read when wrapped in the plastic bag, which couldn't be read moments before. The uniform thickness of .003 mil which the bag extends the stripe away from the worn down read head allows the sensing equipment to now read single magnetic pulse transitions. So when you are shopping and find this fix to be effective, tell the gound-down-gap story to the manager and to treat this as good business advice to speed up register lanes by replacing the mag-stripe read-head in their faulty equipment.

The card age or encoding change count doesn't seem to make a difference. Housekeepers access cards are re-encoded weekly are assigned to individuals. Their section keys are old out of date room keys once distributed to guests and returned. I keep my managers access card concealed under my waistband and attached to a spring-reel cord clipped to my belt, it expires at the end of my shift before my weekend. It's REALLY old, was used by the manager before me, and has accepted re-keying several thousand times without fail. It's only difference from the guest keys is they are newer and have the current hotel slogan printed and are without a hole we punched for the cord. The only time I've had a problem with access was after I inadvertently swiped it behind my jacket lapel, and my pinless badge utilizing three neodymium magnets. That scrambled access card re-encoded just fine and still works every week. I have since intentionally rendered room keys useless quite effectively with my lapel badge. Permanent magnets or electromagnetic coils, when energized, are equally effective at reversing the coding polarities, both accidentally and intentionally to encode them.

Society is the cause of the behavior which has the greatest effect on mobiles erasing keys. I haven't locked myself out in years because I always check that I have key in hand before setting the lock. For the same reason, experienced travelers don't misplace their credit cards at check-in because they still have their wallet in hand as a reminder to replace the card before pocketing the wallet and will never be caught of guard by putting down the wallet. So juggling the pen with the folio with the credit card, wallet and now a hotel card-key, combined with the intention to ring a colleague or loved-one reporting successful arrival, more often than not the key and the phone are placed in hand together. As they step away from the desk the call home is placed and in that moment several different forms of electromagnetic fields are established and collapsed in every microsecond. It's those saturated changing fields which do the damage when beside the cardkey.

I've had freshly encoded keys on brand new stock come back after their first ride in the elevator, and contrarily cards made for future reservations on old, scratched, worn, spilled on, as well as abused cards never have a problem. Invariably the keys which the door rejected are reported by business travelers moments after check-in. I've told them this..."I've a doctorate in Computer Science, I've tried rubbing the stripes together with all manner of low and high coercivity to no effect. Even rubbing keys on flexible fridge magnets take some effort to scramble a key. Did you make or receive a call in the elevator on your way to the room?" They always replied affirmative. So just having your mobile next to your room key for a short length of time would be no problem. There are two mobile properties which scramble key cards. One is low and the other absolutely certain. The low Maxwells property is due to our elevator deep in the concrete shoring of the hotel excavated into a cliff cut. The hotel is primarily fabricated of steel beam and reinforced concrete - a grounded Faraday Cage half trapped in earth and well shadowed from the three nearest cell towers. Add onto that the stainless steel on iron frame box of the elevator surrounded by an additional re-bar reinforced concrete shaft. The phone in this situation is going to ping the tower unsuccessfully at first, pump up the transmit current and ping again until successful. With the key mag-stripe in between there is an alternating electromagnetic field which will gently disturb the key. Keeping the key away from the tower seeking mobile solves that problem in our elevator, which probably wouldn't be a problem if the guests were walking the open prairie to their room under a cell-tower. The second one is the most powerful and consistently effective stripe-wiper, and can also be reduced by a simple menu setting. Remember that Alexander Graham Bell wasn't interested in establishing a communications network, he was pursuing technology to amplify for the deaf and hard of hearing - a legacy which continues to this day in telephone access. Good old fashioned desk set phones have a receiver which contains a coil intended for interfacing as a half of an air-core transformer, influencing the other transformer half in hearing-aids. The FCC requires that mobile phones also be similarly equipped and accessible to the hearing impaired. Several mobile devices have a menu setting which can switch off this coil. There is another coil, usually on the back, which is louder and is often implemented as both the ringer speaker and speaker phone. Those two coils, and occasionally the vibrate motor depending on your device are the most effective at erasing your low-coercivity hotel room key-card mag-stripe.
Holding the card together with the phone in the elevator here can lightly scramble the card. If the card is on the phone when it rings, that has certainly been most effective in wiping out the card. Bluetooth earwig users don't return to the desk for replacement cards.

Having mentioned this key/mobile relationship to the guest and re-keyed the card, usually solves the problem. Single stubborn door locks usually indicate either a low battery or a contaminated read head.
However, I've overheard too many times the combination of key to mobile as an explanation abused by front desk staff in the same way that they blame the computer for problems and delays when it's really the ineptitude of the clerk - such as when a guest calls down to extend their stay, the clerk runs the transactions and calls back to say all is clear when they should indeed say "And remember to stop by the front desk to update your keys!" Personally, I always went the extra effort and brought the replacement extended stay keys to the room for a swap. If they couldn't relinquish the old keys, I reminded the guests to carefully keep the new keys separate, not to use the old keys as that will lock out both sets and require a visit to the desk with their ID.

So, it's not the phone near the key card, but how the phone is used while near the card. In order of greatest scramble effectiveness - Receiving a call and ring/notification beats placing a call, over Hands free use which will disturb the encoding far more than vibrate, which is slightly more than the hearing aid coil in the speaker in cheap phones or vibrate less when a metal can covers the vibrate motor, more than searching for the weakest signal, more than the phone pinging a strong signal, over the minimal effects of just walking under a cell tower with the phone on the card. Unpowered phones do nothing to the keys.

Er, no. Scratch that. It's really a huge conspiracy to get cute chicks to spend more time chatting with us lowly, lonely clerks, which we call "intentionally mismade keys."
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