Model 29 Application Notes
Lightning has long fascinated the technical community. Ben Franklin
studied lightning's electrical nature over 2 centuries ago and Charles
P. Steinmetz generated artificial lightning in his General Electric
laboratory in the 1920's. Anyone concerned with premises data
communications needs to worry about lightning. Few worry enough!
High voltage transients caused by lightning and other electrical
disturbances have the easy ability to destroy semiconductor junctions
and thus cause equipment failure. A lightning strike in the vicinity of
data lines can cause induced ground currents that can also do serious
However, coming right down to it, a lot can be done as far as protection
is concerned. In particular, typical leading edge wave-fronts of a
lightning strike rise at the rate of 1,000 Volts per microsecond.
Adequate protection from this particular lightning threat can be
provided by the Model 29 Lightning Sponge- and the protection can
provided at a vary low price.
The Model 29 Lightning Sponge provides protection for all 9 signal lines
in the standard DB9 connector used for the PC Com Port.
The protection provided by the Model 29 Lightning Sponge is particularly
robust. It is realized by providing 600 W avalanche diodes - one for
each of the 9 lines of the DB9 interface.
The Model 29 has a rapid response time - approximately 1nsec.
The illustration above shows the Model 29 in a typical application.
Notice the designations of 'Earth Ground.' This unit and other similar
lightning sponges operate by directing lightning induced currents to
'Earth Ground.' It is important that the Model 22 be grounded properly.
This should be done with a wire that is, at least, 12 AWG. Connection to
cold water pipes probably provides the best ground. However, make sure
that they are metal not plastic. Connection to a plastic pipe doesn't
help. Also beware of connecting to a ground stud in a wall which,
itself, is not connected to Earth Ground.