Security
Many analog phone signals are easily picked up by radio scanners, allowing anyone within range to listen in on conversations (though this is illegal in many countries). Though many such analog models are still produced, modern digital technology is available to reduce the risk of eavesdropping. Digital Spread Spectrum (DSS) typically uses frequency hopping to spread the audio signal (with a 3 kHz bandwidth) over a much wider range of frequencies in a pseudorandom way. Spreading the signal out over a wider bandwidth is a form of redundancy, and increases the signal-to-noise ratio, yielding longer range and less susceptibility to interference. Higher frequency bands provide more room for these wide-bandwidth signals.
To an analog receiver like a scanner, a DSS signal sounds like bursts of noise. Only the base unit with the same pseudorandom number generator can receive the signal, and it chooses from one of thousands of such unique generators each time the handset is returned to the cradle.
Additionally, the digital nature of the signal increases its tolerance to noise, and some even encrypt the digital signal for even more security.
Read more about this topic: Cordless Telephone
Famous quotes containing the word security:
“It seems to me that our three basic needs, for food and security and love, are so mixed and mingled and entwined that we cannot straightly think of one without the others. So it happens that when I write of hunger, I am really writing about love and the hunger for it, and warmth and the love of it and the hunger for it ... and then the warmth and richness and fine reality of hunger satisfied ... and it is all one.”
—M.F.K. Fisher (b. 1908)
“The horror of class stratification, racism, and prejudice is that some people begin to believe that the security of their families and communities depends on the oppression of others, that for some to have good lives there must be others whose lives are truncated and brutal.”
—Dorothy Allison (b. 1949)
“I feel a sincere wish indeed to see our government brought back to it’s republican principles, to see that kind of government firmly fixed, to which my whole life has been devoted. I hope we shall now see it so established, as that when I retire, it may be under full security that we are to continue free and happy.”
—Thomas Jefferson (1743–1826)