Thanks for reply PIX. That was the thread I read too.
I did some google work and found Patents (EP1107548 etc) where battery change can happen during call. Not sure if that got used in a mobile.
Funny comment, made me laugh:
“Thirdly, give a break to the MS designers 🙂 Tomorrow you will say MS should even work when the internal battery dies out OR even when the DL SS is less than -160dB :)”
What you mean you haven’t done this already, you must be on very long holiday :-)))