[Gta04-owner] Turning on microphone produces loud audio feedback

[Radek Polak]

Hi,
always when i try to turn on microphone, e.g. with

amixer set 'Analog Left Main Mic' cap

it starts giving very loud audio feedback. I suppose that for GSM call i need 
to have both earpiece and microphone turned on. Is there a way how to avoid 
this feedback? Or could someone give steps how to make GSM call with working 
input and output at the same time?

One more and less important question. The earphones that shipped with GTA02, 
will they (at least partilaly) work?

Regards

Radek