All - especially Roy, I said that tounge-in-cheek just to have a little fun. I'm as old? as the rest of you geezers, and even have the circular slide rule mentioned below. My wife's father gave it to me. If you've never seen one, they are really cool. I actually used it in class for a week or so(with an HP backup for tests)when I was in college. You can imagine the interest it engendered. I especially enjoyed Kim H.'s response. Ken -----Original Message----- From: Michael Smith [mailto:michael@xxxxxxxxxx] Sent: Friday, September 13, 2002 10:37 AM To: kimgh@xxxxxxxxx; Ken.Cantrell@xxxxxxxxxxx Cc: Roy.Leventhal@xxxxxxxx; vishrampandit@xxxxxxxxxxx; cpad@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: RE: [SI-LIST] Slide Rules. (Was Re: We ought to address mutual SI-EMI issues in this forum) To keep the fun slide rule thread going... The mystery of the slide rule was based on the fact that if Z = X * Y then log Z = log X + log Y. Therefore if you had a two log scales which could slide against one another, you could measure the addition of the logarithms of two numbers and the result would be proportional to the logarithm of the multiplication of the original two numbers. Other math functions like division could be derived using logarithms in a similar way. If you match the lengths of the two logarithms being added to the required resultant logarithm then you have performed a square root.... Slide rules in a rotating circular scale form are still used today by student pilots. They are used to quickly perform speed/time/distance as well as fuel calculations in the cockpit during cross country flights. These "flight computers" are guaranteed never to run out of batteries and they never have signal integrity issues in any weather conditions. And now back to our regularly scheduled signal integrity issues. Cheers, Michael Smith Hardware Engineer iZ Technology Corp. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Kim Helliwell Sent: Friday, September 13, 2002 8:47 AM To: Ken.Cantrell@xxxxxxxxxxx Cc: Roy.Leventhal@xxxxxxxx; vishrampandit@xxxxxxxxxxx; cpad@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Slide Rules. (Was Re: We ought to address mutual SI-EMI issues in this forum) On Friday, September 13, 2002, at 07:08 AM, Ken Cantrell wrote: > > Roy, > Excellent summary and opinion, I'm sure all agree. I've got just one > question: > what is a slide rule? Hmmmm, how old are you, sonny? A slide rule was an archaic device, made of bamboo, plastic, glass, and metal. It's what passed for a calculator in my college days. Geeks (then known as "eggheads") of my day wore them on their belts, much as they later wore their calculator holsters. Slide rules could not do addition; that was presumed to be something a human could still do in those days. But they could multiply, divide, take logs, do square and cube roots, calculate trig functions and exponentials, etc. Calculations were done by manipulating a center slide, lining up marks ruled on the slide with marks on the stationary portion; then lining up a transparent cursor with a ruled line over other marks to read off the results of a calculation. How the slide rule enabled one to make such calculations is still something of a mystery; results were seldom very accurate. Depending on where on the scale your calculation was located, you could achieve accuracies only of just over 2 decimal places to (nearly) four places. But often the last place was mostly a matter of squinting and guesswork. Slide rules required no batteries or other "power" source, other than the hands required to push the slide and cursor around. There were no buttons or displays required. In fact, it seems incomprehensible that such a thing could ever have existed, let alone been used for hundreds of years. Today, sightings of slide rules are rare. They might be found in museums, in the ruins of old aerospace buildings, or forgotten at the bottom of a grizzled old engineer's drawer. Slide rules once ruled, but have been supplanted by battery powered electronic calculators and spreadsheets. Technology marches on.... Big :-), just in case! > > Ken Kim Helliwell Apple Computer kimgh@xxxxxxxxx 408 974 9936 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu