Wired Wireless Cordless
Wired Wireless Cordless
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Panasonic KX-TCA60 Hands-Free Headset with Comfort Fit Headband List Price: $14.95 Sale Price: Too low to display Used From: $7.49  |
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Designed for use with any cordless phone possessing a standard 2.5 mm jack, Panasonic's KX-TCA60 is an excellent way for you to talk hands-free while you work. Its boom-style microphone adjusts to an optimum level for your mouth... |
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PYLE-PRO PDWM100 - Dual Function Wireless/Wired Microphone System List Price: $53.99 Sale Price: Too low to display Used From: $16.89 |
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Pyle-pro pdwm100 dual function wireless microphone systemcan also be used as a wired microphone; unidirectional; 3 position switch; detachable microphone antenna; operation range: 45 ft90 ft; signal led indicator; telescoping receiver antenna; includes 12-ft xlr to 1/4 microphone cable & 4-ft 1/8 to 1/4 audio cable. |
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Panasonic KX-TG1062M DECT 6.0 Corded/Cordless Phone with Answering Machine, Metallic Gray, 2 Handsets List Price: $89.95 Sale Price: Too low to display Used From: $60.19 |
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Panasonic KX-TG1062M Dect 6.0 Cordless/Corded Phone with Answering Machine |
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Logitech M570 Wireless Trackball List Price: $59.99 Sale Price: $44.00 Used From: $38.88 |
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Your coffee table. Your favorite chair. Your comfy bed. Now there's no limit to where you can get precise cursor control. This hand-friendly wireless trackball lets you work and play wherever you want... |
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Logitech Wireless Wave Combo Mk550 With Keyboard and Laser Mouse (920-002555) List Price: $79.99 Sale Price: $54.99 Used From: $34.93 |
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An ergonomically designed keyboard with a comfort wave design and a contoured laser mouse, the logitech wireless wave combo mk550 gives you a comfort curve without the learning curve. |
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Plantronics M214C Headset with Adjustable Volume List Price: $15.99 Sale Price: $9.36 Used From: $11.95 |
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Designed specially for use around the house, the M214C Headset provides an economical, hands-free solution for taking calls on your cordless or cell phone while you attend to your many duties. Whether youre working from home or racing through household chores, this headset lets you talk hands-free, eliminating the neck strain that can be caused by balancing your cordless handset or cell phone on your shoulder. |
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Logitech Wireless Performance Mouse MX for PC and Mac List Price: $99.99 Sale Price: $63.66 Used From: $42.99 |
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Performance mouse MX wireless |
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Honeywell RCWL300A1006 Premium Portable Wireless Door Chime and Push Button List Price: $49.99 Sale Price: $29.95 |
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The Honeywell RCWL300A P3 Premium Portable Wireless Door Chime and Push Button makes it easy to replace your home's generic doorbell ring with a chime tune that better fits your individual style. This chime is also compatible with a wide range of optional security accessories that can help you safeguard your home and family, and it comes complete with a pre-programmed bell push button... |
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Logitech Wireless Combo Mk520 With Keyboard and Laser Mouse (920-002553) List Price: $59.99 Sale Price: $41.19 Used From: $36.89 |
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The logitech wireless combo mk520 puts convenience and control comfortably at your fingertips thanks to its full-size keyboard with concave keys and hand-friendly, contoured laser mouse. |
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Plantronics MX500i 3-in-1 Headset List Price: $59.95 Sale Price: $22.99 Used From: $18.99 |
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The MX500i 3-in-1 Headset from Plantronics delivers high-performance sound for clearer calls at home. Experience reduced wind and fast motion noise along with optimal sound clarity with the pivoting WindSmart microphone... |
All About Cordless Telephone
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 within 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 used to power the cordless handset. Placing the cordless handset in the cradle in the base unit recharges these batteries. A period of 12 to 24 hours is required for recharging the batteries.
With features like cell handover, data transfer and international roaming (on a limited scale), the once clear-cut line between mobile telephones and cordless telephones (telefone sem fio) has now 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 common sight. But that is not the case. Actually, higher frequencies have been seen to exhibit worse propagation in ideal case. There is also a tendency for the path loss to increase with higher frequencies. Locally varying factors such as antenna quality, signal strength, the modulation method being used and interference are more influential than other factors.
With Landline telephones working on a bandwidth of about 3.6 kHz (a small fraction of the frequency that a human ear can interpret), the transfer of audio is carried out with an audio quality that is just enough for the parties to communicate each other. Because of this limitation in the design of the phone system itself, it is not possible to improve the audio quality beyond a particular limit in cordless telephones.
Most of the good-quality cordless telephones (telefone sem fio) try transferring the audio signal with lowest possible interference and greatest possible range. Even the best of the cordless telephones fail to match the audio quality that a high quality phone wired to a good telephone line provides.
Sidetone (echo of voice heard in the speaker of the receiver), disturbing constant background noise that is due to the cordless system, and inability to obtain a full frequency response that is available in a wired phone are few of the reasons for a not-so-good audio quality. Rare exceptions, obviously, always exist that sound unbelievably similar to a wired telephone. But even these are considered as `fluke` by most industry standards.
Higher frequency is now being used in other home products like the microwave oven, Baby monitor, Bluetooth, wireless LAN, etc. Thus, cordless telephones (telefone sem fio) using higher frequency may face interference from signals from these devices.
Eavesdropping is a constant 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 used to take care of this kind 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 thousands of options.
DSS generates a signal spread that leads to a kind of redundancy, which gives rise to increased signal-to-noise ratio. It also leads to increase in signal range and decreases interference susceptibility. It is easier to use this kind of wide-bandwidth security option with higher frequency.
This article is under GNU FDL license and can be distributed without any previous authorization from the author. However the author's name and all the URLs (links) mentioned in the article and biography must be kept.
About the Author
This article can also be accessed in portuguese language from the Article section of page www.polomercantil.com.br/telefone-sem-fio.php
Roberto Sedycias works as IT consultant for www.PoloMercantil.com.br