Hi Russell,

RB>A lot of good surge protectors do ....NOT
RB>The common ones have a triggering voltage of 270Vac, so in my oppinion
RB>the extra 30Volts has already stuffed your equipment, before the
RB>Varistor is triggered.
RB>If lightning strikes at your modem through the power or phone lines,
RB>do you think that the super spark that just jumped 10 miles through
RB>the sky is going to be stopped by a spark arrestor with a gap of a few
RB>microns or a wafer of composite material in a varistor.

I live up in the mountains midnorth coast N.S.W.,
our farm is on granite surrounded by copper ore.
we get some lightening, le' me tell yu.
My last modem - Zoltrix FM-VOC144I copped a few hits.
The two 270 Vac varistors disintigrated - replaced,
the two AC filter ceramic caps to ground,
one blew to bits, one blew short circuit - replaced,
ringer relay stuffed - replaced,
one track vapourised - rewired,
no worries.

These hits caused an old style phone to ring,
and blew up a cheapy phone.
Fortunately no damage to the old 386.

Experience with line equipment, etc has shown me
that with inductance etc, ring voltages can exceed 100 V.
and safe design practice is to allow for 240 Vac.
Components designed for 240 will take more than 30 V extra.

When you get a hit or suspect you've been hit,
test and REPLACE suspect protection devices.

It's not the extra 30 volts but the dv/dt and power of the transient.
Most of the transient should be shunted to earth through ac coupling
capacitors. The varistor has a finite turn-on time, also can absorb
only a certain amount of energy (converted to heat, etc).
The line fuses will blow before a protection device.

Have a good earth connection, screw the internal modem in securely.
The lightening energy should go direct to earth
through ac coupling - chassis - power cable,
not through your i/o bus - power supply - power cable to earth.
or be converted to heat by the varistor, & maybe some sound,
mechanical distortion, etc.
Sometimes accompanied by the device releasing it's store of smoke,
which is a designed into all electronic devices!

The 300 mil isolation gap between the line devices and the
guts of your computer are sufficient to stop thousands of volts.

Don't you just hate Murphy's laws.

Play safe, disconnect phone lines and 240 V power cables
before a storm hits.

p.s. I'm protected by God too.

Yours,
Colin.
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