First, if incoming was a phone line, then what was the
outgoing path? Without both incoming and outgoing paths, then
no damage can happen. Second, how do you explain why a
transient completely ignored that telco provided 'whole house'
protector? Phone line typically has surge protection. AC
electric typically does not.
Did a transient enter on phone line, damage modem, then
stop? Of course not. That would even violate primary school
science lessons. Before damage occurred, first a complete
circuit was conducting. Electricity flowed from cloud to
earth via those modems. Only after the complete circuit
conducts through everything in that circuit, only then did one
part become damaged. Where that damage happened does not
define the incoming path. It only defines what was in that
destructive circuit.
An AC electric transient that passes through modems
typically damaged a modem's DAA section. It is, after all,
where galvanic isolation causes highest energy dissipation.
The DAA section is on phone line side of a modem; and often
damaged by surges incoming on AC electric. This from one who
repairs surge damaged modems (even back in the 1200 baud days)
by first tracing a surge path, and then identifying all failed
components. In fact, this modem was repaired after an AC
mains surge damaged its DAA section.
Damning evidence. I not only defined theoretically why
modems are damaged by incoming transients, but also repair
them at the component level - experience also cited.
Again, until one can say why a telco provided surge
protector did not earth the incoming transient, then one
cannot claim modem was damaged by phone line. You can only
speculate that an AC electric transient found earth ground via
that phone line. Incoming modem destructive transient was
from AC electric; outgoing to earth ground on phone line.
Another's technical analysis to the same conclusion:
http://groups.google.com/[email protected]
or
http://tinyurl.com/yqgv
Review your facts. Some IC pins on that serial port card
make a direct connection to one AC mains wire. Use a
multimeter to confirm it if you don't believe it. A direct
connection that bypasses computer power supply. AC mains,
through serial port card, through modem, to earth ground via
phone line. Again, did the surge enter serial port card from
modem, damage card, then stop? Of course not. Serial port
card was in the same destructive circuit as modem. Follow the
path of that surge from AC mains to earth ground via phone
line. Because there is not 'whole house' protection on your
AC mains, then AC mains is a perfect (and usual) path for
surge damage - the complete electrical circuit. How many more
reasons need I post? Another ten? These are damning facts
base on fundamental principles and decades of personal
experience.