[Sigi_BC84]

hrothgar said:

The main thing that I learned about these phones is not to apply concepts like "common sense" to cell phone architecture.

True for many real-world computer architectures.

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In actuality, the designers want people to think that thye could improve recption. The external antenna was completely transparent. The "real" antenna was a U-shaped coil built into the casing.

I always kind of doubted the usefulness of the extendable antennae of many cell phones (even more interesting to hear that from someone with inside knowledge). OTOH many phones had stub antennae that you could screw off the case which definitely reduced reception (I owned several such phones). AFAIK it took them a while to build the antenna into the case while keeping below the allowed thresholds for radio pollution of the user.

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Another interesting little data point that I learned about many small embedded devices is that they are "always" on. If you turn the device off, you shut down the GUI and a many of the more power hungry applications. However, a lot of the basic functions (like Bluetooth) are still up and running.

Well, of course the phone is not completely turned off otherwise you couldn't turn it back on with a soft button as is and the built-in alarm clock would fail on you as well.

However, to actually locate a phone it would either have to be:

• booked into a cell -> clearly not the case when turned off
  
• continously emitting a signal strong enough to be triangulated from a distance (space or cars with special equipment)

Now, the energy necessary for option two would drain the phone empty in no time even if turned off.

No, I'm not buying this.

--Sigi

[mike777]

that is why I wonder if the police could send an activation signal and boost up the radio transmitter, which is always transmitting anyway, correct? Anyway we will all be wearing RFID tiny tiny chips

"Real-time tracking of cell phones is possible because mobile phones are constantly sending data to cell towers, which allows incoming calls to be routed correctly. The towers record the strength of the signal along with the side of the tower the signal is coming from. This allows the phone's position to be easily triangulated to within a few hundred yards."

It seems enough power is always generated so incoming phone calls can be received. That means cell phones are always on and always tracked Yes?

[Sigi_BC84]

mike777, on May 23 2006, 12:14 AM, said:

"Real-time tracking of cell phones is possible because mobile phones are constantly sending data to cell towers, which allows incoming calls to be routed correctly. The towers record the strength of the signal along with the side of the tower the signal is coming from. This allows the phone's position to be easily triangulated to within a few hundred yards."

This only applies if the phone is turned on and logged into one (or more) cells of the network.

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It seems enough power is always generated so incoming phone calls can be received.  That means cell phones are always on and always tracked Yes?

If the phone is booked into the network, there is at least one cell (usually more) that is in contact with the phone. The network has certain information about signal strength of the phone so the provider can estimate how far the phone is removed from the cell(s) in question. If the phone is connected to at least three cells, signal triangulation can be done to locate the phone within a certain area. This won't be very exact though, since the perceived signal strength of the phone does not correspond perfectly with the distance to the cell (there are buildings, atmospherical disturbances and other irregularities involved).

A reasonably accurate pinpointing of the phone is presently only possible if the phone receives GPS signals and transmits them back somehow. (GPS signals are coming from satellites in orbit and have to be decoded by special receivers on earth). NB this is not possible if the phone is turned off.

It is especially hard (not to say impossible) to locate the phone when it is turned off, and I'm not expecting having to stand corrected in that regard...

--Sigi

[barmar]

Sounds like some people are confusing turned off (can't make or receive calls) with hung up and the lid closed (can receive calls, but can't make calls or use other functions). Perhaps because most people never actually turn off their cell phones, and may not even realize that they can (there's often no separate on/off button, you typically have to hold down the End key for several seconds). I have a cell phone that I only use on special occasions (I got it mainly to keep in touch with prospective partners and dinner companions when I go to NABCs), so I turn it off most of the time, but I believe this is quite atypical.

[mike777]

Ok I contacted a very old buddy of mine who has worked with Motorola for 23 years in cell phones to see if we can get some answers such as what does on or power on really mean. What can be tracked or not tracked.

Geez he worked there for 23 years and I still remember him as a litttle kid . And I used to live across and down the street from the corp headquarters in Schaumburg.



"When a phone is "off" there is no way to know where it is.

When you turn a cell phone "on", to goes into standby mode. The lights and display may blank out after a few seconds to save power, but the phone is "on" and ready to receive phone calls. Hitting any button will usually bring the backlight and display on so you know when the phone is "on".

A few seconds after you turn the phone "on" it will "register" on the network. This is a quick transmit burst to a nearby cell to let the network know you're available to receive incoming calls, and roughly where the calls should be routed. This allows the network (Cingular,Verizon, etc) to limit the routing of an incoming call to a several square mile area until it finds your exact cell location (which it finds when the phone responds to the incoming call paging request).

Since you may be moving wile you're in standby, you may have moved into a different cell area from the time you registered to when you get an incoming call. So the network pages you over a several cell area to find you to connect the call. In networkspeak that area is called a "paging area".

Although I don't get involved with the network side or police investigations, if a phone is turned on, it could remotely be asked to re-register on a network at anytime, which would isolate the phone to a specific cell...but this is still a couple square mile area. But the phone does need to be "on" for this to work. You can't turn it on remotely.

Recently, there are new requirements for emergency 911 services in cell phones that use cell tower triangulation to locate a phone (and hence a distressed user) in 911 situations to better resolutions. I'm not that up on whether this can or has been used by law enforcement to track criminal activity. If so this would isolate the user's position to a few hundred yards or closer. But again, the phone must be "on".

Hope this helps."

[barmar]

Many cell phones also have GPS receivers in them, although the user may be able to disable it through the Options menu. When enabled, if the phone is "on" it knows precisely where it is, and can transmit this information to the 911 operator.

[rbforster]

mike777, on May 23 2006, 01:51 PM, said:

Recently, there are new requirements for emergency 911 services in cell phones that use cell tower triangulation to locate a phone (and hence a distressed user) in 911 situations to better resolutions. I'm not that up on whether this can or has been used by law enforcement to track criminal activity. If so this would isolate the user's position to a few hundred yards or closer. But again, the phone must be "on".

A police friend in a big city tells me they don't have access to the 911 location stuff even for emergencies(!), but I'm sure whoever lobbied for the new 911 tracking is keeping all the location logs. If you're afraid of your cell phone, remember that any conducting metal sheath/box/etc will block ALL incoming and outgoing signals (see the Wiki for Faraday cage).

[Sigi_BC84]

barmar, on May 23 2006, 04:44 PM, said:

Sounds like some people are confusing turned off (can't make or receive calls) with hung up and the lid closed (can receive calls, but can't make calls or use other functions).  Perhaps because most people never actually turn off their cell phones, and may not even realize that they can (there's often no separate on/off button, you typically have to hold down the End key for several seconds).  I have a cell phone that I only use on special occasions (I got it mainly to keep in touch with prospective partners and dinner companions when I go to NABCs), so I turn it off most of the time, but I believe this is quite atypical.

Hmm, nowadays most pieces of electronic equipment are not completely turned off at anytime. "Turned off" means that the device is in standby mode (cf. TV sets that are still listening for the remote control when "off").

Now I think most people are actually aware of this since usually a standby indicator of some sorts is involved (lit red lamp or clock display). The mobile phone companies call it "standby" when the phone is actually properly turned on. This has nothing to do with the standby of household electronics people got accustomed to.

So actually the correct analogy would be:

• TV set with power cord unplugged <-> Mobile phone with battery removed (or completely drained) -- the "real off".
  
• TV set in standby (red light still glowing) <-> Mobile phone turned on but not in "active" use. This is somewhat inexact because the phone in standby is still doing more work than a TV (or notebook computer) in standby.
  OR Mobile phone turned off (but reacting to soft button to turn it back on).
  Whatever you think is suited more to the general feel of users.
  
• TV running <-> Mobile phone in use (making calls, accessing the internet, etc.)

Another point is that Hollywood movies don't exactly contribute to user education in that regard. The main thing that was bugging me when watching into the first series of "24" was that Jack Bauer always had perfect reception with that tiny earplug he was wearing (except for dramatic reasons when it became convenient for the script author to make him lose contact with the villain). Another baaaad example is the movie "Enemy of the State" (with Will Smith). Yuck.

Still I think you are exaggerating when you are saying that most users don't know that there is another level of "turned off" with their phones. Why? Because as soon as the battery drains completely you will see that there is. So maybe many users stop thinking about it and sooner or later forget about the distinction.

I for my part wasn't even aware that there could be confusion about this when making my original post.

--Sigi

[Sigi_BC84]

Sigi_BC84, on May 31 2006, 01:37 AM, said:

TV set in standby (red light still glowing) <-> Mobile phone turned on but not in "active" use. This is somewhat inexact because the phone in standby is still doing more work than a TV (or notebook computer) in standby.
OR Mobile phone turned off (but reacting to soft button to turn it back on).
Whatever you think is suited more to the general feel of users.

Actually I was making an edit here when I was seeing that I was shifting into the "wrong mindset" myself:

Technically, of course the second analogy is appropriate (TV in standby <-> Mobile "turned off"). Along these lines, "TV running" maps to "mobile phone turned on" not really mattering if you are making a call or not.

--Sigi