1. Many surge suppressors will protect only against low energy transients, AND WILL ALLOW HIGH ENERGY TRANSIENTS TO DIRECTLY REACH THE "PROTECTED" EQUIPMENT.
2. Some surge suppressors may be fire hazards.
A severe wind storm passed through my area recently. My modem, plugged into a "LIME" surge suppressor, was damaged when the 120 volt line voltage experienced a surge that I'd guess to be in the 200-250 volt range. (see note below) I expect surge suppressors to provide protection extending into the kilovolt range, so when the modem was damaged by such a low voltage event I investigated the construction of the surge suppressor.
I was AMAZED to find that the suppressor contained internal fuses which could blow but still allow power to be delivered to the computer! With the fuse blown, all protection is lost. SINCE BEGINNING THIS INVESTIGATION I'VE FOUND SEVERAL OTHER SURGE SUPPRESSORS THAT ARE FUSED IN EXACTLY THE SAME WAY. A simplified diagram of the surge suppressor circuit is shown here:
The MOV is the surge suppressing component, a Metal-Oxide Varistor. The LED is normally lit by the voltage appearing across the MOV. Under excess voltage conditions the MOV will conduct a surge from the hot line, through the fuse, to the neutral line, thereby protecting equipment plugged into the outlet. The fuse is provided because the MOV may "give its own life" to protect the downstream equipment, and when MOVs die they usually become a short circuit and may explode (see note 3).
The circuit above protects only against high voltage, low energy transients such as might be caused by other equipment on the same circuit switching on and off. High energy transients will pop the fuse and continue on into the equipment that's supposedly protected! The high energy transient might not have sufficient voltage to damage the "protected" equipment itself but, with the fuse blown, the equipment will be vulnerable to even low energy transients on the line.
MOVs can provide save, effective protection in a properly designed circuit. For example:
Now the MOV protects the load at all times. The fuse is sized to carry the full load current and the circuit breaker can be eliminated. The quarter-sized MOVs that are usually used in inexpensive surge suppressors are not appropriate for use in this circuit, though. If the MOV fails, the fault current will almost certainly explode that small MOV at the same time it blows the fuse. MOVs large enough to withstand the fuse-blowing fault current are easily available. They will provide even BETTER protection against the common, high voltage, low energy transients than the standard MOVs provide, but they cost more.
Recommendations:
1. Examine all your surge suppressors. Discard any that have no UL listing mark, they could be a fire hazard. 2. Consider the degree of protection you need. If ALL your computer equipment is always switched off (or, even better, unplugged) when storms threaten, your exposure to high energy surges in minimal. You will PROBABLY get enough protection from one of the better inexpensive surge suppressors, MOST of the time. If, on the other hand, you cannot assure that all your equipment is off the power mains when high energy surges threaten, investigate the internal circuitry of the surge suppressors before buying, then invest in a good one. 3. Install serious surge suppression on the phone line feeding your modem too. Because the phones work at much lower power levels than the computer, fuses and MOVs can be sized much smaller than they are for the power lines. In fact, the quarter-sized MOVs that I said may be inappropriate for use in a power line suppressor are well suited to application on a phone line. Be sure the phone line suppressor and the power line suppressor share a good short ground path.
Richard C. Akeson on Exec-PC BBS or (414) 377-4335 (voice)
Notes:
1. My estimate of 200-250 volts as the surge voltage is based on an observation that incandescent lamps subjected to the same surge became very bright for 100 to 500 mS and some of them burned out. Voltages in the 200-250 volt range would produce these effects, and could be produced by the cross-phase line faults characteristic of windstorms.
2. Many inexpensive surge suppressors provide no fuse upstream of the MOV, although some do provide a circuit breaker. In either case the MOV in such a device may be expected to explode if it is driven to failure.
3. I refer above to MOV's "exploding", some clarification may be in order. An MOV is a small, non flammable, non explosive device, but it can dissipate only a limited amount of energy in any time interval. When full line voltage is impressed across a failed MOV, the MOV will be forced to dissipate several kilowatts. Dumping this kind of energy into a device the size of a quarter makes the device REAL hot, REAL quick. The MOV will usually vaporize, coating everything around with a soot-like substance. There will usually be a small flash or fireball, and frequently there will be enough heat to partially melt or deform the case of the surge suppressor that contains the MOV. If there are flammable materials near the MOV, they may be ignited. Especially in the case of a large MOV in a small surge suppressor case, the fireball flash and ejected "soot" may extend well outside the surge suppressor case.
If UL is doing their job, they will have tested a surge suppressor under MOV-failure conditions to determine that there is at least a reasonable degree of fire safety. Look for the UL listing mark before buying.
SILVER!
Sent to us by Colin Brown
What you should know BEFORE you purchase
STERLING SILVER JEWELRY!
If you are attracted to the cool and crisp white luster of STERLING SILVER jewelry, you join a tradition that spans many centuries and crosses a multitude of cultures . . .
Love of this precious metal can be traced as far back as the ancient Greeks and Egyptians. Egyptians not only proudly wore sterling during their lifetimes, but they also requested that their favorite sterling jewelry be entombed with them! Greek warriors used both gold and silver for adornment on breastplates and other articles of war; and they also amassed private collections for their own use.
Advancing to highly practical useage, silver was the base of most common coinage in North America from the 16th Century until 1965. After that year, it became too valuable for use in coinage. Today, silver along with the other precious metals of gold and platinum, is used extensively in medicine and dentistry, in industrial applications ranging from TV sets to telephones, computers to calculators, and most recently in the space program.
Eventually, in the late 1970's, there developed a combination of economic circumstances and new fashion trends which would render the gleam of silver more desirable than ever before.
The economic circumstances were the soaring prices pf gold and platinum, proportionately raising the prices of jewelry in these metals. At the same time, fashion tastes were changing . . . bold and dramatic designs in clothing and accessories were conquering the fashion world. Many jewelry designers began to enjoy creating large bold pieces at very affordable prices. Its cost advantage makes silver more adaptable to fashions of chunky cuff bracelets and gigantic earrings which in gold, would be expensive. Thus, sterling silver has now become a favorite medium for some of today's most creative and innovative designers.
HOW DO YOU KNOW IF IT'S STERLING SILVER?
The United States government has the highest standards in the world for classifying sterling silver. Because pure silver is not as strong a metal as 14KT gold or platinum, it must be hardened by adding copper in varying proportions. In order to qualify as "sterling silver", a piece of jewelry must contain 92.5% silver and 7.5% copper. Jewelry that meets this requirement can be stamped ".925 sterling" . . . the mark of quality.
Lesser qualities of silver are used and sold outside of the United States, and they are marked either ".875" or even ".750". The signif- icance of these lesser purities is appreciated when you compare the polishing qualities of each . . . the most desirable "white" gleaming finish is accomplished only with the .925 silver. Also, the "patina" (the quality or glow of the metal after it has been worn) of .925 silver far surpasses the lesser purities.
Some sterling silver jewelry is plated with a coating of gold that is 120/one-millionth of an inch thick to produce "vermeil" (pronounced ver-may) which is often used in high-design pieces.
HOW TO CARE FOR STERLING SILVER JEWELRY
First and foremost, always keep your sterling silver jewelry seperated in a compartmentalized jewelry box. This protects against scratching. Unlike gold, silver can react to particles in the air and develop a tarnish which is known as oxidation. It does, however, deteriorate like iron-based metals or copper. This film can be easily removed and, if you wear your sterling silver jewelry constantly, it won't tarnish!
Some tips for cleaning:
* A simple at-home method is to wash the jewelry under the hottest water your hands can stand, rubbing in a bit of soap and/or toothpaste and rinsing under the same hot water. The water will bead up and only has to be patted dry.
* There are many silver polishes on the market today, and one need only follow the instructions on the bottle or jar to achieve the desired results. Ask your jeweler to recommend a brand.
SUMMING UP, STERLING SILVER HAS ITS OWN DISTINCT PERSONALITY . . .
IT CAN BE CASUAL . . . IT CAN BE ELEGANT . . . IT CAN BE TRENDY . . .
AND IT CAN BE CLASSIC!
IN WHATEVER THE MOOD, ITS COOL AND CRISP WHITE GLOW MAKES A POWERFUL FASHION STATEMENT.
RUBY BEGONIA
By Del Freeman
"Wedding Bell Blues"
In my somewhat checkered youth, I was briefly and bitterly wed to Grunt, the gung-ho ex career Marine hun. With the passage of time, I've often examined that union, hoping to find something nice to say about him. Even the worst of us will do a noble and fine thing occasionally, my grandfather used to say, and Grunt was no exception - he left me.
Other than that, I'm hard pressed. I can't even remember what it was that so fascinated me about Grunt in the first place. He showed up on my doorstep wearing black and white spectator shoes in an era when only the nerdiest of wimps would have been caught in them. Long after sundown. Dead.
There he was in all his radiant glory. Aside from the two- tone footwear, all his clothes looked like he bought them at "The Movin' Man." Grunt glowed in the dark long before Elvis Presley.
Grandma took one look at those spectator shoes, declared that she'd once been enamored of a lovely young man who wore spectator shoes, and decreed Grunt acceptable. I thought Grunt was a geek.
Little did Grandma suspect, Grunt was just barely on the ride side of the law. He kept showing up on the doorstep wearing those shoes, persistence personified, taking his clues from Zelda's pursuit of Dobie Gillis. I almost got a reprieve when Grunt was apprehended borrowing someone's hubcaps without the owner's knowledge or consent. The Judge took one look at Grunt, figured him for a potential hot-sun-rock-breaker doing 20 to life, and offered him three squares and a cot, either in the service or in close confinement.
No choice at all for my boy. He rushed out and bought combat boots, shaved his head and joined the Marines. They were looking for a few good men, and apparently Grunt fooled them.
The man became a saint almost before the sun set on his hairless pate. It was like a miracle the way he went from delinquent to dedicated serviceman, obviously suffering a memory loss along the way. To this day, he can't understand how our eldest and loveliest, child of his loins, could be such an incorrigible. I tell him it's all that intermarrying of first cousins in his family, but he likes to blame it on my side of the family. Claims that because my father and grandfather are both signpainters, we're all crazy. Says it's from smelling the paint fumes. You can see what an impossibly unreasonable fellow Grunt has turned out to be.
Since our disassociation, Grant has managed to raise two other incorrigibles without my help, but he figures it's bad blood on his second wife's side.
Anyway, he did his 20 years with ease. Once he had become a saint it was all high cotton for him. I hear he spit shines his tenny-runners and squares off at corners to this day.
I believe it, too. Grunt is a seriously serious fellow - all the time. In fact, only once did I hear of him ever saying anything even mildly amusing, and that was an accident.
In a moment of unbridled passion during his early delinquency, Grunt had my name tattooed on his forearm. Now Grunt had a lot of flowers tattooed over the names of other girls he had formerly been enamored of, and by then people were asking him to stand in front of florist shops for advertisement. Perhaps because he'd used up all acceptable flora, he never got around to having my name covered over.
Driving down the road one day years later with our daughter in the car, his youngest incorrigible, then eight years old and unable to read, (obviously it's that cousin thing), asked, "Dad, what does that say?"
Completely expressionless, and with his own uniquely characteristic lack of humor, Grunt replied, "Mistake."
