On Mar 22, 6:33*pm, Jon Elson wrote:
wrote:
The power spikes can come from anywhere. I personally experienced
equipment destroying spikes that came from the telephone wires. A
construction company was excavating very deeply for a sewer pumping
station near my office. Somehow they connected 220 volts to the buried
telephone cable. The power went through the local phone company
junction box and into our phone system and fax machine. The surge
protectors immediately absorbed all the power they could and produced
smoke. Then the power continued on to burn out circuit boards in the
equipment.

I have a fairly expensive business phone system in my house, central
control box and stations here and there. *So, I made my own protector.
I used a 10 Ohm 1 Watt film resistor in series with each incoming phone
wire, and then connected to a 3-terminal gas tube arrestor. *The idea is
the film resistors blow like ultra-fast fuses during a severe surge,
allowing the gas tube to handle what got through before. *This has
worked well, I've never had any damage to the phone system, but the DSL
modems I used to use got blitzed a couple times. *The resistors did get
popped a couple times, too. *I don't think you can get this kind of
phone wire arrestor anywhere as a complete unit, except maybe from a
telephone physical plant supplier. *The gas tubes can be bought from
Digi-Key and similar electronics distributors.

I have had some other gear damaged, but due to the nature of the
equipment, I am pretty sure it was NOT from anything coming in the power
lines. *Wires running from one end of your house to the other can
develop thousands of Volts when there is a nearby lightning strike, due
to magnetic induction. *I've had some stuff in my home burglar alarm
damaged, as well as an ethernet port on a computer. *(Most of this
damage all happened in one incident, nearby lightning strike.)

So, I'm not so sure that power line protectors will actually prevent a
whole lot of damage.

Jon

You don't have to be so sure. The IEEE and NIST are though.