Re: full duplex or half duplex

mike7411@xxxxxxxxx wrote:
What if two phones keep trying to send a very positive signal?

Won't they keep stepping up the voltage?

Ideally, all that happens is the two signals add, and whatever
the sum is, is what each receiver produces for sound output.
That would mean that if you and I are talking at the same time
on the phone, we may or may not be able to understand what the
other person said... :-) (No different than if we are talking
to each other across a lunch table, and do the same thing.)

However, there is an interesting catch that you might enjoy to
idea of. If the two phones are a *long* distance apart, the
signals can do some strange things. That is because the signal
from your voice can actually be reflected from the distant end,
and come back over the circuit. If the time it takes to do that
is very short, your ears can't hear it. But if it is long
enough to affect your ears, it starts sounding as if you are
talking into a drainage ditch pipe! If the distance is *really*
long (for example when a geostationary satellite system is used,
and the distance is 23,000 miles each way to the satellite), you
can actually say "boo", and then hear the entire word echoed
back at you.

As long as the echo is *weaker* than the original, what you'll
hear is not just one "boo", but a series of progressively weaker
ones as it echoes back and forth. On the other hand, if the
echo is actually *stronger* than the original, you'll hear maybe
one boo, and then it will start squealing with probably a single
tone (but possibly it will do strange things, with a tone that
changes pitch, and one common description is "motor boating"
because that is what it sounds like).

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@xxxxxxxxxx
.

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