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Emission levels are complicated. There isn't a particular threshold they have to be under. Rather, phones negotiate with the tower to use the minimum power needed to get their signal through, depending on their distance from the tower and other factors. Using lower power means less interference with other phones as well as increased battery life and less RF absorption by the user's head. This negotiation has a lot of parameters that vary between carriers, so carriers legitimately need to test that every model and version of phone works reliably on their network and doesn't just start blasting at full power sometimes, causing other calls to drop.



Also phones (and towers?) in border areas have some logic to avoid roaming onto the other country’s network.

This leads to lots of misconceptions too.

With a local Rogers SIM from a high building in Toronto, my phone will only see Canadian networks on a network scan. But when I put in an EU SIM, same phone and same place, a network scan will see several US networks and even prefer connecting to them (probably cheaper roaming rates), even if the connection is ultra-weak.

Feels like there’s some geo-fencing preferencing, or maybe time-distance bounding going on.


> There isn't a particular threshold they have to be under.

This is a patently false thing to say.

https://www.fcc.gov/general/cell-phones-and-specific-absorpt...


OK, there's a super-high limit 100x greater than what phone hardware is capable of putting out. But that's not what carriers are testing -- they want to see that it only uses say 0.5 mW, not 1 mW, when close to the base station.


Under 1.2 W/kg in 10g of tissue ICNIRP is the international standard.

India has its own in 1g of tissue but I don't know the threshold value off the top of my head.


Modern phones don't even get close to that limit at full power. Still, it seems prudent to minimize transmit power for safety.




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