Cell phones intentionally
radiate at specific frequencies, which are outside the aviation bands. The problem is that all electronics produce unintentional noise at other frequencies. Even a simple motor generator can radiate at high frequency if it is not built correctly. Another example is your computer. It is not intended to radiate at all(barring wireless, etc.), but it does have high speed electronics inside. The CPU, bus, modem, and all sorts of other components inside are blasting out EM waves at a number of different frequencies. That's why your electronic devices have stickers on them saying that they comply with FCC Part 15.
There are other issues, like phase and frequnecy shifting due to propagation medium, susceptibility ranges, and cable shielding but I will skip that.[/quote]
Can you explain to me what is meant by "This device must accept any harmful interference, even if it will cause undesirable operation"? This statement has always confused me.
Now for the reason I came here.
My school system recently "invested" in a lot of Promethian Boards
, which are like electronic whiteboards. They're pretty damn awesome, but I think there are a lot of better uses of the money. Anyway, one of the things you can do with them is give the students these "eggs" which are just devices with buttons that say "A","B","C","D","E", and "F." The teacher can have a question on the board and the students can answer by pressing the buttons, and the board will record that. When it shows the results the board shows the percent who got it right, the percent who got it wrong, and the percent who "didn't know." After a few questions someone asked what was meant by "didn't know", and the teacher replied that those were the students who didn't answer. Since we had extras, there would always be some in that category. Later in the class someone asked "How does the egg know that you didn't know the answer?"
In history we were discussing how the U.S. Government can't give titles such as knight, and we talked about that for about five minutes. At the end the teacher said something like "There are no k---nig---hts in the U.S." (the Monty Python pronounciation.) A student then asked what a "k---nig---ht" was. This one isn't exactly stupid, as everyone can't be expected to know the reference. However, in the context of the discussion it would be reasonable to be able to determine the meaning easly, instead of repeatedly asking what that meant.