On Jan 21, 2007, at 21:59, David Schulz wrote:
hey, sure, of course i have checked the cat5 first, but it is
clearly not the cable. id say it is as ted has written. what i
would like to know now is how exactly happens this "hardware
The interface chips use a very low level "protocol" to identify the
rates and modes being used by the other end. Those are dependent on
voltage thresholds which sometimes are not as accurate as one would
like. Components age and tolerances change which can cause the two
ends to get out of sync with each other. The interface
specifications also tend to change a bit over time. I don't have the
exact specs for ethernet, but the same issue arose many years ago
with RS-232 devices. The original specification had a threshold
voltage of around 20 volts. For line drivers with 25-28 volt sources
it worked great. But, 25 volts is somewhat difficult in many
situations and people started fudging using 12 V sources which would
work with many of the drivers that actually used a 10 V threshold.
Those devices would interface with some, but not all of the older
devices. Ethernet has undergone a number of changes from the
original RG-8 cabling to today.
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