A cordless telephone (telefone sem fio) is an electronic telephone that comprises of a wireless handset and a base unit. Communication is carried out between the handset and the base using radio waves. The wireless handset can be operated only inside a fixed range from its base unit. The range of operation is generally within 100 meters. The base unit needs electricity to power it. Batteries are utilized to power the wireless handset. Placing the wireless handset in the cradle in the base unit recharges these batteries. A time period of 12 to 24 hours is required for recharging the batteries.
With functions like cell handover, information transfer and international roaming (on a restricted scale), the once clear-cut line between mobile telephones and cordless telephones (telefone sem fio) has now been combined by the contemporary cordless telephone standards.
Frequency bands have been designated in each country for cordless telephones (telefone sem fio). Advertisements by manufacturers claiming that there is an improvement in audio range and quality with greater frequency are a typical sight. But that is not the case. Actually, higher frequencies have been seen to demonstrate worse distribution in perfect case. There's also a tendency for the path loss to increase with greater frequencies. Locally varying factors like antenna quality, signal strength, the modulation technique being utilized and interference are more important than other elements.
With Landline telephones focusing on a bandwidth of around 3.6 kHz (a small fraction of the frequency that a human ear can interpret), the transport of audio is done with an audio quality that is just adequate for the parties to communicate each other. Because of this restriction in the design of the phone system itself, it is not feasible to improve the audio quality past a particular limit in cordless telephones.
Most of the good-quality cordless telephones (telefone sem fio) attempt transferring the audio signal with lowest possible interference and best feasible range. Even the very best of the cordless telephones are not able to match 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 is due to the cordless program, and inability to acquire a full 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, usually exist that sound incredibly similar to a wired telephone. But even these are regarded as as `fluke` by most business standards.
Higher frequency is now being utilized in other house products like the microwave oven, Baby monitor, Bluetooth, wireless LAN, etc. Thus, cordless telephones (telefone sem fio) using greater frequency might face interference from signals from these devices.
Eavesdropping is really a continuous security threat for analog telephones. Any one with a radio scanner and within range can pick up these signals and listen to conversations. Modern digital technology is thus being utilized to deal with this type of unauthorized access.
DSS (Digital Spread Spectrum) utilizes 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 is sensible only to that base unit which has the same pseudorandom number generator as the cordless handset. Every time the cordless handset is returned to its cradle, a brand new unique generator is chosen from thousands of choices.
DSS generates a signal spread that leads to a type of redundancy, which gives rise to improved signal-to-noise ratio. It also leads to increase in signal range and decreases interference susceptibility. It's easier to make use of this type of wide-bandwidth security choice with higher frequency.
With functions like cell handover, information transfer and international roaming (on a restricted scale), the once clear-cut line between mobile telephones and cordless telephones (telefone sem fio) has now been combined by the contemporary cordless telephone standards.
Frequency bands have been designated in each country for cordless telephones (telefone sem fio). Advertisements by manufacturers claiming that there is an improvement in audio range and quality with greater frequency are a typical sight. But that is not the case. Actually, higher frequencies have been seen to demonstrate worse distribution in perfect case. There's also a tendency for the path loss to increase with greater frequencies. Locally varying factors like antenna quality, signal strength, the modulation technique being utilized and interference are more important than other elements.
With Landline telephones focusing on a bandwidth of around 3.6 kHz (a small fraction of the frequency that a human ear can interpret), the transport of audio is done with an audio quality that is just adequate for the parties to communicate each other. Because of this restriction in the design of the phone system itself, it is not feasible to improve the audio quality past a particular limit in cordless telephones.
Most of the good-quality cordless telephones (telefone sem fio) attempt transferring the audio signal with lowest possible interference and best feasible range. Even the very best of the cordless telephones are not able to match 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 is due to the cordless program, and inability to acquire a full 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, usually exist that sound incredibly similar to a wired telephone. But even these are regarded as as `fluke` by most business standards.
Higher frequency is now being utilized in other house products like the microwave oven, Baby monitor, Bluetooth, wireless LAN, etc. Thus, cordless telephones (telefone sem fio) using greater frequency might face interference from signals from these devices.
Eavesdropping is really a continuous security threat for analog telephones. Any one with a radio scanner and within range can pick up these signals and listen to conversations. Modern digital technology is thus being utilized to deal with this type of unauthorized access.
DSS (Digital Spread Spectrum) utilizes 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 is sensible only to that base unit which has the same pseudorandom number generator as the cordless handset. Every time the cordless handset is returned to its cradle, a brand new unique generator is chosen from thousands of choices.
DSS generates a signal spread that leads to a type of redundancy, which gives rise to improved signal-to-noise ratio. It also leads to increase in signal range and decreases interference susceptibility. It's easier to make use of this type of wide-bandwidth security choice with higher frequency.
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