[joezydeco]

No, it's just a chronic lack of sidetone in these devices.

Sidetone is the small amount of feedback in the earpiece as you speak into the microphone. The telephone company figured this out 100 years ago and then, somehow, we totally dropped it when mobile phones came along. We've been shouting into microphones ever since.

[wkat4242]

They also used to feed some noise even when no sound was received. Softphones still do this today, it's called comfort noise :) if you have none most callers start wondering if the connection is still active.

[the-dude]

Isn't the 'somehow' this? With POTS, both parties were transmitting on the same line but on digital/mobile connections, there are 2 streams?

[joezydeco]

Yes, there are two streams. But the handset could provide sidetone directly to the earpiece if it wanted to.