I thought I read in this newsgroup that the difference between the 4th and the 5th ed. was that it reflects the latest Cisco test which no longer deals with the 1900 switch.
I see in the book that the 1900 switch is still there. So what's the difference? And is the 1900 switch still on the exam? Anybody know?
I also found an error in the book. Or at least an omission. Page 38, Spread Spectrum Wireless LAN. "(Spread Spectrum) It's a wideband radio frequency technique that the military came up with that's both reliable and..."
The military knew nothing of this until Hedi Lamar gave it to them, patent and all. She doesn't get near the credit she should. She invented it, she patented it, and she gave it to the military as her contribution to the war effort. And the patent expired well before the cell phone industry picked up the technology.
"NetWorker" > difference? And is the 1900 switch still on the exam? Anybody know?
"Spread Spectrum" I beleive comes in two flavors, "frequency hopping," the original WWII variety, and "direct sequence encoding - psn" which was first commerically patented by Equatorial COmmunications in the 1980's.
On Fri, 13 May 2005 04:28:41 GMT, NohWarezMann wrote:
I Googled "Hedy Lamarr"+"Spread Spectrum" and got:
Hedy Keisler Markey aka Hedy Lamarr
Who invented the spread-spectrum (formerly called "frequency-hopping") concept? None other than Hedy Lamarr, made famous by her starring role in Ecstasy, a very x-rated movie, filmed in Czechoslovakia in 1933. Hedy Lamarr invented in 1940 and patented in 1941, under her married name of "H. K. Markey", US Patent number 2292387, granted in Aug. 1, 1942, "Secret Communication System", filed June 10, 1941. She signed it "Hedy Kiesler Markey." Kiesler is her maiden name. Gene Markey was her second Husband's name. Lamarr is her stage name. Her full name is Hedwig Eva Maria Kiesler. She unwittingly disguised herself by not employing her stage name. It is only this year (1997) that the connection has been pointed out by Dave Hughes. At present, Hedy Lamarr lives in retirement in Florida. Each of the two aforementioned applications of the spread-spectrum communications concept was shrouded in military secrecy, at the time. We just knew the concept; but the identity of its originator was not disclosed to us, under the restriction of "need to know". The US Government was the assignee of the Patent; thus, legally, it was the owner of the concept. It had no reason to disclose to us, and we had no "need to know", the originator of the Patent. Currently, the spread-spectrum radio transmission is employed extensively in both civilian and military communications: Radio links with many satellites, portable telephones which operate in the 900 MHz region, wireless network connections, high-density cellular-telephones, ... Belatedly, Hedy Lamarr deserves credit for her stroke of pure genius in inventing the spread-spectrum concept in one evening, out of thin air! She deserves to be admitted to Mensa, as an honorary member.
This patent was granted in 1942, but the details were a closely held military secret for many years. The inventors never realized a dime for their invention; they simply turned it over to the US Government for use in the war effort, and commercial use was delayed until after the patent had expired.
Hedy Lamarr died on Wednesday 19-th January 2000, in Florida, USA.
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Here is a copy of the original spread spectrum radio patent co-invented by Hollywood movie actress Hedy Lamarr and composer George Antheil. It was based on the frequency-hopping concept with the keys on a piano representing frequencies, and the subsequent frequency shifts to music.
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# Hedy Lamarr - George Antheil 'Secret Communications System Patent, by Chris Beaumont An article by George Antheil's son, including GIFs of the original patent.
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# The Principle of Spread Spectrum Communication, by Jack Glas. A very readable overview of Spread Spectrum in mostly mathematical terms. Explains why SS is jam-restistant, and also explains the difference between Frequency Hopping and Direct Sequence variants of Spread Spectrum.
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# Wireless Field Test Project Reports, by Dave Hughes of Old Colorado City.
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# Not Just Another Pretty Face, a biography of Hedy Lamarr Includes a biography and a bibliography.
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