On 9/30/2015 2:27 PM, Ralph Mowery wrote:
"Don Y" wrote in message
...
Ground is never ground. A nearby lightning strike can have "ground"
bounce, considerably. Note that there is a huge magnetic event
("EMP") associated with a lightning strike. This "induces" voltages in
conductors -- even buried ones!

Note that these "disturbances" can follow conductors into equipment
attached at both ends.

I've arranged for each of the network drops, here, that is accessible
"on the outside of the house" (though still part of this same building)
to have protection from lightning -- as well as tampering/vandalism
(e.g., you wouldn't want someone to "do something" to an accessible
ethernet drop and take down some/all of your network infrastructure
because they were of a hostile intent!


Right, there are two ways to do it, half-assed and hope for the best. That
will stop some of the slight misses. Then you can do it the right way and
probably spend more than the equipment it is worth.

One of the better way is to make sure all the ground rods are tied together
with wires as short and direct as possiable.

Just check the insurance and see how much is covered by the lightning.

In my case, I also have to consider "malicious acts" -- what if a
thief/vandal decided to use the *accessible* network drop as a means
of injecting something "unexpected" (malicious packets, high voltage
disturbances, etc.) *into* my control fabric in the hope of
confusing/crashing the devices that govern the control of the
house (e.g., alarm system, among others).

The same reasoning extends to my avoidance of wireless protocols
(someone can eavesdrop or inject traffic without having to be
*on* the property -- can also "jam" my communications resulting
in a denial of service style attack.

When I design gaming (gambling) devices, this is a very real
possibility: "patrons" hoping that by doing something
"unexpected" they can "trick" a machine to "pay out" when
it otherwise would not.

Obviously, if such an exploit was "productive" (for the thief!),
it wouldn't take long for word of it to "make the circuit" and
render the gaming device "undesireable" (i.e., lost sales!)