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
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