But is that from research or does a person with a phone know whether their phone has communicated with a tower or not at a given time? I think the person I was replying to was somebody else, and she said she didn't know about Apple but that her Android phone pinged when it was switched off. Like it was something that was evident from the phone itself.As far as I know
a smartphone sends information about its IMEI number and the SIM card placed in it to the nearest towers with GSM transmitters.
When a signal is sent to three nearby towers, the location of its source can be determined.
It happens b/c there is a battery inside that supports some systems that need electricity so that they don't hang up.
And the phone, even turned off (via the button) but with the battery inserted sends a signal to a nearby antenna.
JMO