Displaying Withheld Numbers

Channel Hopper

Just recalling something prompted by Simbas post.

A few years ago I was told that mobile phones had an internal code that could be used by the emergency services to trace activity (triangulation within cells). Additionally if the phone was registered with a valid address it could be used to make emergency calls without a Sim card.

Now that 1984 has passed it wouldn't surprise me that the authorities might be utilising the location aspect on potential suspects, and the witheld number system may be overridden in certain cases.

There is a very fine line between "hobby" and "mental illness"

Analoguesat

Triangulation is easy enough - unless you are in a very remote area the phone will be picked up on 3 or 4 phone masts. Then its an easy job to work out where it is from the time delays at each mast - the more masts its picked up on the better the triangulation

Analoguesat's message to the world Analogue forever!

huntingtigers

I also reside in London, would you care to divulge a specific shop that performs this service. Thanks

BombedOne

I don't know what about UK, but here such service is avalable for major operators, and is called AntiCLIR.

p.laver

I would also be interested in any info, I've googled 'AntiCLIR' but can't find any info in English

BombedOne

CLIR=Caller Line Identification Restriction.

In short - regardles who and how calls you, your phone operator ALWAYS knows his phone # - because he has to bill it, if he can't identify the number, there's will be no connection. But, if the flag CLIR (delivered together with incoming ringtone) is set to on, the phone won't show the number. Some old phones just ignore the CLIR flag, so they are able to display witheld numbers.

Other way to ignore CLIR flag, is to make certain request via USSD, so phone company will disregard CLIR signal, coming to your number. In past, the software that was used by phone companies had some backholes, so it was possible to activate CLIR rejection without any payment. Now these holes are fixed, so you have to pay.

Here's link to my phone company page, where's some info about this service in english:

_ttp://www.magticom.ge/index.php?section=93&lang=eng