"I believe while the cockpit is sterile (til 18,000 ft)"

I thought all the electronic equip was supposed to be off below 10000 feet but I could be wrong , they're supposed to tell you when it's ok to turn them on, sometimes they don't . Same with the other airlines I've flown. They have no way of knowing what sort of electronic gadgets people bring on board and a few could be harmful , like a transceiver so to play it safe the airlines make everybody turn everything off.
Funny though , i always leave my BoseQC2 turned off but hanging around my neck during take off which seems like it should violate a safety rule cause my neck could get injured but they never say anything about that so it must be okay.