Phones have been the center point of means of communication for many years. Phone was invented by Alexander Graham Bell after a lot of trial and error in 1870. Invention of the phone, as it is called today, began with transmitting speech electrically. Telegraph and telephone are both wire based electronic systems. Telephone was a result of efforts by Mr. Bell to perfect the telegraph. This was in great demand as vocal communication was possible between two individuals. It was an unheard phenomenon and people criticized it as much as they accepted it.
Phones were a large and stationary piece of equipment and were able to communicate only between specified groups of individuals. Since then, phones have been improvised upon and made to look attractive, sleek and are a handy device. Engineers made use of lighter and durable materials in an endeavor to make phones portable and efficient. By 1950s, phones had become quite efficient and were not so cumbersome any more.
Cordless Tool
A lady named Teri Pall invented the cordless phone in 1965. She was a jazz singer by profession and came up with an idea to eliminate the wiring and make the handset wire free. Such a cordless phone functioned at a low frequency of 47-49 MHz and worked well only in small areas. Advanced versions of higher frequency cordless phones are capable of functioning flawlessly in large spaces. Efficiency of high frequency phones is superior to that of low frequency phones with better security as it became difficult to interfere into calls.
Federal Communications Commission or the FCC granted permission to companies to manufacture 900 MHZ frequency phones only by 1994. This move by the government triggered an upsurge in the demand for cordless phones. Frequency of 900 Mhz was ideal to scrap out static caused by walls, appliances and interference in signals by other objects. They provided high quality sound output but were still prone to eavesdropping. In order to tighten security, FCC allowed manufacturers to make phones with frequencies of 2.4 GHZ and 5.8 GHZ.
These are secured cordless phones and cannot be interrupted by any radio scanner. High end cordless phones evolved primarily keeping in mind the confidentiality of conversations.
Christmas Sales DEWALT Bare-Tool DC390B 6-1/2-Inch 18-Volt Cordless Circular Saw 201
Dec 22, 2011 17:59:22
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Christmas Sales DEWALT Bare-Tool DC390B 6-1/2-Inch 18-Volt Cordless Circular Saw Feature
- 3,700 RPM for fast rip cuts and cross cuts
- 6-1/2-inch carbide tipped blade for 2x cutting capacity at 90 degrees and 45 degrees
- High strength magnesium shoe and upper guard provides increased durability
- 0-50 degrees bevel capacity provides additional capacity for a multitude of applications
- Fan-cooled motor with replaceable brushes for maximum power and durability; tool only, no battery
Christmas Sales DEWALT Bare-Tool DC390B 6-1/2-Inch 18-Volt Cordless Circular Saw Overview
The DeWalt DC390 is a 18V cordless circular caw (and is the tool only). The saw uses 6-1/2 inch carbide tipped blade for 2x cutting capacity at 90 and 45 degrees. It has high strength magnesium shoe and upper guard provides increased durability. 0-50 degree bevel capacity provides additional capacity for a multitude of applications. It features fan-cooled motor with replaceable brushes for maximum power and durability.SAVE NOW on Christmas Sales Offers below!
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| This Christmas DEWALT Bare-Tool DC390B 6-1/2-Inch 18-Volt Cordless Circular Saw is cheap and shipping as well. |
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