Cell Phone Tower Scanning
Q.: When a cell phone is turned on, and pings for a tower, do all towers record the pings, no matter the
service provider?
For instance, if your provider is Verizon, will your pings be recorded by a Cingular tower if it is the
nearest in the clear?
A. (From Mark van der Hoek)
Nope. First of all, the phone doesn't 'ping' anything, it scans intelligently. When your phone is first turned on, it searches for available service according to a list that it stores internally. This list includes the frequency band and operator ID to scan, and it will scan ONLY these for normal service. (911 calls are different.) Your own operator and any authorized roaming partners will be in the list, but nobody else.
When it locates the best signal from list, it locks on, then registers on the network by sending its serial number and mobile number. This registration is sent to ONE site on ONE operator, not to all in the area. This is to let the system know you are available. The system then knows you are there, and where to send paging messages if there is a call for you. It stores this info until you either move to another area, or de-register. (Your mobile will re-register every X minutes. If the system doesn't hear from you for X minutes, it will assume you've turned off your phone and will forget about you until you re-register. X can run from a few minutes to an hour or more. The typical values are about 10-15 minutes.) Other than the system knowing your registration state, and the area you're in (or your last registered location), there is no record kept of this. Every time your registration area changes, the old info is overwritten. No history is kept. If a call comes in while you are de-registered, it will be sent straight to a "treatment," in phone company lingo. This would be voice mail, if you have that service, or a "Customer not available." recording, if you don't. (So, if you call someone and it goes straight to voice mail or a recording, it's usually because they are de-registered.)
A Verizon phone neither knows nor cares about a Cingular site, and vice versa. They use different technologies, and there is no compatibility between them. (CAVEAT: Some Verizon phones and some Cingular phones have analog capability. In this case, the 911 scenario, below, does apply.)
If you had, for example, a Verizon phone and Verizon & Sprint in the same area (same technology), the only time Sprint would ever be aware of your phone might be during a 911 call. If your phone can't find a good signal on a Verizon site, it will use whatever it CAN find (within the same technology), and that carrier is obligated to process the call. So, back to Verizon & Cingular, if you have an analog capable Verizon phone, and no Verizon service is available, Cingular could process that call if they had analog in your area.