With features like cell handover, information transfer and international roaming (on a limited scale), the as soon as clear-cut line between mobile telephones and cordless telephones (telefone sem fio) has been blended by the modern cordless telephone standards.
Frequency bands have been assigned in each country for cordless telephones (telefone sem fio). Advertisements by manufacturers claiming that there is an improvement in audio range and quality with higher frequency are a typical sight. But that's incorrect. Actually, higher frequencies have been seen to exhibit worse distribution in perfect case. There's also a tendency for the path loss to improve with greater frequencies. Locally varying factors such as antenna quality, signal strength, the modulation method becoming used and interference are more important than other elements.
With Landline telephones working on a bandwidth of about 3.6 kHz (a little fraction of the frequency that a human ear can interpret), the transport of audio is carried out with an audio quality that's just adequate for the parties to communicate one another. Because of this restriction in the design of the phone program itself, it isn't feasible to enhance the audio quality beyond a particular limit in cordless telephones.
The majority of the good-quality cordless telephones (telefone sem fio) attempt transferring the audio signal with lowest feasible interference and greatest feasible range. Even the best of the cordless telephones fail to fit the audio quality that a high quality phone wired to a great telephone line provides.
Sidetone (echo of voice heard in the speaker of the receiver), disturbing constant background noise that's due to the cordless program, and inability to obtain a complete frequency response that is obtainable in a wired phone are couple of of the reasons for a not-so-good audio quality. Rare exceptions, obviously, always exist that sound incredibly comparable to a wired telephone. However even these are regarded as as `fluke` by most business standards.
Greater frequency is now becoming utilized in other house products like the microwave oven, Baby monitor, Bluetooth, wireless LAN, etc. Therefore, cordless telephones (telefone sem fio) using higher frequency may face interference from signals from these devices.
Eavesdropping is really a continuous security threat for analog telephones. Any one having a radio scanner and within range can choose up these signals and listen to conversations. Modern digital technology is thus being used to deal with this type of unauthorized access.
DSS (Digital Spread Spectrum) makes use of frequency hopping, i.e. spreading up of audio signal over a wider range in a pseudorandom fashion. DSS signal sounds like noise bursts to a radio scanner or any other analog receiver. This signal makes sense only to that base unit which has the same pseudorandom number generator as the cordless handset. Each time the cordless handset is returned to its cradle, a new unique generator is chosen from a large number of choices.
DSS produces a signal spread that leads to a kind of redundancy, which gives rise to improved signal-to-noise ratio. It also leads to raise in signal range and decreases interference susceptibility. It is easier to use this kind of wide-bandwidth security choice with higher frequency.
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