[guardian-dev] signal without sim ?

[shmick at riseup.net]

how does the following make sense

android phone *without* sim & aeroplane mode *on*

network: unknown
signal strength: -51dBm
mobile network type: UNKNOWN:0
service state: radio off

android phone *without* sim & aeroplane mode *off*

network: unknown
signal strength: -81dBm (fluctuating strength; stationary phone)
mobile network type: EDGE:2
service state: out of service

i thought in aeroplane mode all radios were off and you could, depending
on the phone, enable wifi, bluetooth selectively, etc

but where is the signal strength coming from - i thought a phone could
not associate/ping a cell tower without a sim *unless* making an
emergency call

also why does a phone without a sim last immensely longer (in my case)
than compared with aeroplane mode with a sim ?

can/do phones ping/associate cell towers/base stations in aeroplane mode ?

can/do phones ping/associate cell towers/base stations without a sim ?

(probably, if your phone is ownd anything is likely)