1. Ours are in the back galley and thus there is no switch in the flight deck. It will turn itself on with a large enough G Force or by coming into contact with water, or it can be manually turned on by the Cabin Crew.
What has ELT location to do with manual override? If they can put a wire from the cockpit to the ELT on one airline's 737NGs, they can do it on yours.
And it can obviously work and still transmit in water , but does it have a certain depth cut off?
I think it's generally agreed that it will not work underwater at all at the frequencies it transmits, especially in sea water which is particularly conductive (electrical conductivity is a bad thing for a radio waves).
Citing this reference...
http://users.tpg.com.au/users/ldbutl...munication.pdf
There is an attenuation formula...Decibel loss per meter) = 0.0173 x the square root of (frequency x conductivity). It is more than 10db per meter in sea water at VHF frequencies. At ELT UHF frequencies, it is over 50db/meter. This is assuming the transmitter and antenna cabling is absolutely watertight.