Wikipedia:Reference desk/Archives/Science/2016 March 23

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March 23

Hospitals inhibiting cell phone signal

I was at a hospital and noticed that my cell phone was getting no signal despite the hospital being in a major (population in the millions) city of a modern industrialized country with generally excellent cell phone coverage. I'm aware some hospitals have a rule not to use cell phones over concerns, founded or unfounded, over cell phones having a small possibility of interfering with medical equipment, but a nurse whom I was talking with told me something I found surprising: she claimed that the hospital not only had a rule banning cell phone usage, but that I was getting no signal because the hospital was somehow inhibiting cell phone signals to prevent anyone from circumventing their rule. Also, I did notice that I got a strong signal outside the hospital, but no signal inside the hospital, though this is not decisive evidence.

So does this actually happen, urban hospitals somehow inhibiting cell phone signals? If so, how widespread is this practice? And what technique or technology does the hospital use to accomplish it? (Deliberate siting in a dead zone outside the range of cell towers? Walls of some particular shape or material? Cell phone jammers? Some other method?)

—SeekingAnswers (reply) 09:03, 23 March 2016 (UTC)

Laws will differ based on jurisdiction, but in the U.S., according to the Federal Communications Commission's website, "Federal law prohibits the operation, marketing, or sale of any type of jamming equipment, including devices that interfere with cellular and Personal Communication Services (PCS), police radar, Global Positioning Systems (GPS), and wireless networking services (Wi-Fi)." - Nunh-huh 09:28, 23 March 2016 (UTC)

My suggestion: The hospital is built with reinforced concrete and they used "energy saving" windows which are designed using a metall film or mesh. The result is very bad reception. And if the policy is that cell phones shall not be used indoors then no repeaters will be installed. Practical things to check 1) is the reception good just outside the door? or if you open and stand in a window? 2) What kind of windows do they use? It may also be that the operators have commanded their equipment to drop cell phones in that sector. Ferrofield (talk) 20:32, 26 March 2016 (UTC)

• A cell phone jammer would be totally self-defeating in a hospital, since it releases exactly the kind of interference that the hospital wants to avoid. Smurrayinchester 09:29, 23 March 2016 (UTC)

There' no evidence cell phones cause that sort of problem. Interestingly in Britain they tried to bring in some special phones for the emergency services - and they were shown to cause interference! Also they had bad coverage so were a bad idea. I'd have thought there should be some way to have call interception so only emergency service or other authorized calls are allowed. Surely it should be possible to stop people taking their phones out every three minutes and yapping loudly where they shouldn't -- they can go outside first using those appendages called legs if they want to do that. Dmcq (talk) 10:35, 23 March 2016 (UTC)

If they wanted to really curb the use of cell-phones, they would block them (not actively jam them). Although I doubt this is a huge issue. It appears to be just a case of making the safe bet. --Scicurious (talk) 22:00, 23 March 2016 (UTC)

How would you block them? That is the question. —SeekingAnswers (reply) 23:48, 23 March 2016 (UTC)

I have no idea what the reason is, but the observation is credible and it would be interesting to hear more. For example, you might have been under interfering material (some kind of metal shielding for an X-ray station on the next floor up?). Conceivably, a nearby cell phone tower could refuse to continue a connection with you based on triangulation of your position or by spying on GPS in the phone - I don't know if this software exists but it could certainly be written. In that instance I imagine that More Important People Than You would have some special code or their phone numbers on a whitelist or something. Wnt (talk) 11:27, 23 March 2016 (UTC)

The hospital could be a giant Faraday cage. Use metal sheeting on (or within) the walls and roof and glass windows with a thin metal coating. The latter may be used anyway, as they provide better thermal insulation. I know of a building that was an accidental Faraday cage. The architect liked a metal sheeting exterior. After complaints of no or bad cellphone reception (depending on provider), they considered installing signal repeaters. I don't know whether they actually installed them. I imagine this type of hospital building may have been popular in the Cold War, as it is also immune to EMP. PiusImpavidus (talk) 11:33, 23 March 2016 (UTC)

Come to think of it, although most serious medical conditions in a private prison are treated with ibuprofen, prisoners are occasionally brought to hospitals for treatment. This implies that a hospital building's primary purpose is to serve as a prison. Cell phones in prison describes some of the sort of software I was hypothesizing; and I think it is obvious that preventing malingering prisoners from violating incommunicado would be ranked far above any possible medical or personal concern you might have. Wnt (talk) 11:42, 23 March 2016 (UTC)

Your statement makes no sense. You state that occasionally, a prisoner is taken to a hospital to be treated. Then you state that the primary purpose of the hospital is to be a prison. That literally does not follow logically, since the prisoners are in no way the primary population of the hospital... --Jayron32 13:09, 23 March 2016 (UTC)

My assumption is that if one prisoner coordinates an escape or calls up and threatens a victim or orders a hit, heads will roll. If tens of thousands of people complain that they couldn't update their relatives on what's happening, heads will not roll. Wnt (talk) 15:05, 23 March 2016 (UTC)

Wow. In a world full of horses, you really are only capable of seeing zebras. Or unicorns... --Jayron32 18:35, 23 March 2016 (UTC)

This BBC report on the subject shows that there are definite problems in real hospital equipment from real cellphones. It goes on to point out that the phone has to be really close to the equipment to have an effect. I think the conclusion is that phones should be turned off inside treatment areas - but should be fine out in the corridors and waiting rooms.

OK - so that's the pragmatic approach - but you could understand (given the importance of the matter) that in an abundance of caution, they simply apply a blanket rule. That same BBC article says that 64% of doctors admitted that they use cellphones in the hospital in violation of the rules...and that NO deaths have ever been attributed to cellphone interference with hospital equipment.

This FCC page says that it's illegal to block or jam cellphones - and doesn't mention an exception for hospitals. But let's suppose there were some kind of exception made:

• Clearly (as User:Smurrayinchester points out), jamming the signal would be a stupid idea because the jammer would (by necessity) put out more power in those frequencies than the cellphone itself).
• Passively blocking cellphone signals with a Faraday cage around the whole building would actually be counter-productive because the cellphone will gradually increase the power of it's transmissions to the absolute maximum in a failed effort to reach nearby cell towers - so this would be a great way to guarantee the maximum possible radio noise!
• More intelligent (and probably cheaper/easier/more practical) would be to put the faraday cage around the treatment areas to at least shield radio noise from corridors and such - but since we already know that the phone has to be within a few feet of the sensitive equipment, that would also be pointless since the only problematic devices are those INSIDE the treatment areas.

So I VERY much doubt that this hospital was intentionally either jamming or blocking your cellphone. Being in the middle of a large steel and concrete building - possibly on the margins of reception for some other reason - might be enough to produce the effect you're seeing - but I very much doubt that the hospital authorities had done this deliberately. Large/heavy equipment such as body scanners and X-ray equipment could have blocked the signal - and it's plausible that some kind of electromagnetic emissions from such devices was unintentionally interfering with your phone. Either way, moving a hundred yards from that spot ought to have gotten your better reception. Did you actually try that? SteveBaker (talk) 14:16, 23 March 2016 (UTC)

Re: "Either way, moving a hundred yards from that spot ought to have gotten your better reception. Did you actually try that?": I didn't stay in a single spot. After hearing what the nurse told me, I got curious and went all over the hospital, and even to different buildings of the multi-building hospital. My cell phone normally has no trouble getting a signal inside large buildings, but at this hospital, I couldn't get a signal anywhere inside the hospital buildings, but could outside. —SeekingAnswers (reply) 17:34, 23 March 2016 (UTC)

The cell phones in prison article links this product, which apparently is not a cell phone jammer. On the other hand, I found this report of cell phones blocked in a hospital in Ireland due to an adjacent prison with cell phone jamming. Wnt (talk) 15:13, 23 March 2016 (UTC)

I am not sure that a jammer or Faraday cage would prevent a cellphone from interfering with nearby equipment. Would the phone still transmit (perhaps in short, infrequent bursts) as it looks for a nearby tower? Or would it simply listen for the tower and not transmit a reply until it finds one? --Guy Macon (talk) 15:22, 23 March 2016 (UTC)

Depends. Sometimes it drops into analog modes which will drain the battery quickly. But I find it strange that this topic has gone on so long only because my closest hospital has built in WiFi for the rooms. Now if your in the MRI room or the Xray room, no cell phones are allowed. The cardiac monitors to the nurses station are wireless now as well. I'm sure they don't want you wearing a cell phone while hooked up to the monitor. They even had cell phone charging stations in the ER waiting room. What they really don't want is employees spending the day on social media instead of patient care. Day care centers have stricter policies than the hospitals. Hospitals (at least in the US) want repeat business so ERs and Maternity wards are the nicest and most accommodating places. --DHeyward (talk) 16:06, 23 March 2016 (UTC)

This is tangential, but no modern cell phones have an "analog mode". Analog signalling for cell phones was part of 1G systems, which no modern phones support and which have been taken out of service I think everywhere. What will drain the battery is the phone boosting its transmission power if it can't connect to a tower, to try to connect to towers that might be farther away. --71.110.8.102 (talk) 01:30, 24 March 2016 (UTC)

@71.110.8.102: - Meh, I have an old phone. But seriously, SMS is one of the oldest formats used in pagers ans uses the AT modem command set. Certainly later GSM and 4G LTE have made it digital but I still believe the U.S. with Verizon and others that avoided GSM initially still have some analog service in rural areas and for compatibility a TDMA phone can drop into analog mode. I haven't looked in a while but see if any of those carriers still support TDMA (Qualcomm took over the market with 4G CDMA and FRS is all but gone but I think some of phones still support analog for SMS even if they can't make a call). Pagers still exist. If your phone works in the U.S. but not Europe or Japan, I think it still has analog communication capability. China went CDMA but I think they avoided paying Qualcomm. CDMA licensing dominates Qualcomm earnings. --DHeyward (talk) 07:43, 24 March 2016 (UTC)

Our Advanced Mobile Phone System and History of mobile phones article suggests all analog or digital AMPS was shut down in the US by 2008. As for pagers, our article suggests there are a whole host of different systems used both local and wide and that these systems are usually distinct from mobile phone systems (which is an advantage for numerous reasons). It's not clear to me if any of them are analog, but neither that article nor our Short Message Service article suggests SMS was ever used for pagers (the SMS originated with GSM not with analog networks). SMS may be used for message submission and partly analog systems may have been used to submit SMS (e.g. Telelocator Alphanumeric Protocol) but those are different issues. Getting back to pagers, our article suggests FLEX protocol is the most common one used in the US nowadays at least for wide networks and it seems to be digital. Nil Einne (talk) 18:41, 24 March 2016 (UTC)

It's quite possible the hospital may have taken counter-measures that are counter-productive. The person(s) they assigned the task of ensuring that cell phones can't be used in the hospital may not even be aware of the reason. I like to use the example of speed bumps, which are designed to slow traffic down, to make roads safer. However, when you combine people who see them swerving to avoid them and those who don't see them losing control of their car when they hit them at high speed, they may very well make the roads less safe. StuRat (talk) 17:54, 23 March 2016 (UTC)

No matter where I stand in my apartment, my smartphone registers a low level signal (only two bars), but if I initiate a call, the level immediately increases to maximum (all bars). This implies that the cellphone towers transmit at low level when idle, but increase power when actually interacting with a device. It might be interesting if the OP had initiated a call while inside the hospital - it may have been successful. Most users simply start a call without looking at the level; by checking it he may have been unnecessarily discouraged. Akld guy (talk) 21:24, 23 March 2016 (UTC)

I would expect that cell phones would then adjust the signal meter depending on if it's during a call or not. Perhaps yours has poor software. StuRat (talk) 23:38, 23 March 2016 (UTC)

I do not understand your response. It does not seem to bear any relationship to my suggestion that the cellphone tower increases power. Are you saying that my cellphone should misrepresent the signal level that it receives? This is a 6-month-old Samsung 5 with all available updates installed. Please clarify what you meant. Akld guy (talk) 02:18, 24 March 2016 (UTC)

The cell phone knows if it is currently making a call or not. If it's customary for cell towers to increase power during a call, then the cell phone manufacturers would adjust for that in the signal bar, say by showing twice as many bars, when the phone was not in use. This would make customers happier, since they would see more bars. (Of course, they wouldn't want them to always see full strength bars, as then they would be pissed when they couldn't make a call, and call customer service and complain that their phone was broken.) Think of a voltmeter which has different settings with different sensitivities displayed on the meter. StuRat (talk) 02:28, 24 March 2016 (UTC)

Utter nonsense, sorry. You're asking me to believe that a cellphone that hadn't initiated a call via a celltower could predict the full-power output of that tower? Not only that, but whatever level it predicted would be a misrepresentation. C'monnn. Akld guy (talk) 02:54, 24 March 2016 (UTC)

If there is some standard practice, like cell towers boosting to twice the strength during calls, then the cell phone makers would know that and use it. And it's not misrepresentation, since there are no units listed on the bars. The usual interpretation is that it's a percentage of max. If you have 5 bars possible, then 4 bars is 80% of max, etc. So, if they know what the max cell tower output is under each scenario (during a call or not), 4 bars should be 80% of that max. StuRat (talk) 16:28, 24 March 2016 (UTC)

Your last sentence implies that you're assuming that maximum cell tower power always equates to all bars lit. No more, no less. Well duh, signals can be so strong that they're right off the scale at more than 5 bars, which of course displays can't show because they're limited to 5 bars. Do you have any experience with radio receiver LCD S meters as I do? You're presenting hypothetical situations based on OR theories about cellphone makers misrepresenting signal levels to their customers. Provide some evidence that they manipulate levels. Akld guy (talk) 20:57, 24 March 2016 (UTC)

I've been in our local hospital many times and I can get a signal in only a few areas. I thought that it was probably due to all of the steel used in the construction or all of the electronic equipment, but I don't know. Bubba73 ^{You talkin' to me?} 01:53, 24 March 2016 (UTC)