Comment Re:Hardware Security (Score 3, Interesting) 89
Your friend is most likely lying. The phones in the switch (specifically for QC) would only hear one side of the conversation. If you hear both sides, there was an echo issue (and the conversation wouldn't continue between the two parties).
If the speaker was connected to a local loop, then it would hear both sides. (While I agree it should not have been connected to a local loop, I would not be surprised if (occassionally) it was.)
Phones designed for use with traditional land lines have echo-suppression circuits. As do the equipment at the switching office. This was done to avoid the cost of a third wire and because using either earth or electrical ground was too noisy.
An old design: http://www.epanorama.net/circu...
A somewhat modern design: http://www.epanorama.net/circu...
Also, very early telephone designs did not have echo suppression. I have one that one of my grandmothers bought at an auction (a certificate of legal sale was included with the phone). In theory, it is compatible with the current land line system, though I have never tried it. It is very similar to this: http://oldphoneman.com/images/...