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The transmission of images obsessed inventors as early as 1875 when George Carey of Boston proposed his cumbersome system. Only five years later, the principle of scanning a picture, line by line and frame by frame – still used in modern television sets – was proposed simultaneously in the USA (by W.E. Sawyer) and in France (by Maurice Leblanc). The first complete television system – using the newly discovered properties of selenium – was patented in Germany in 1884, by Paul Nipkow. Boris Rosing of Russia actually transmitted images in 1907. The idea to incorporated cathode -ray tubes was proposed in 1911 by a Scottish engineer, Campbell Swinton.

Another Scot, John Logie Baird, beat American inventor C.F. Jenkins to the mark by giving the first public demonstration of – a dim and badly flickering – television in 1926 in Soho, London. Britain commenced experimental broadcasting almost immediately thereafter. Irish actress Peggy O’Neil was the first to be interviewed on TV in April 1930. The Japanese televised an elementary school baseball match in September 1931. Nazi Germany started its own broadcasting service in 1935 and offered coverage of the 1936 Olympics. By November 1936, the BBC was broadcasting daily from Alexandra Palace in London to all of 100 TV sets in the kingdom.

At the beginning there were many competing standards on both sides of the Atlantic. Baird’s technological solutions were trounced by Isaac Shoenberg and his team, set up in 1931 by Electric and Musical Industries (EMI). RCA refined its own system, as did the Dutch Philips. Not until 1951 were the standards for public broadcasting set in the USA and in Europe.

But the Americans were the ones to grasp the commercial implications of television. Bulova Clock paid $9 to WNBT of New York for the first 20-seconds TV spot, broadcast during a game between the Brooklyn Dodgers and the Philadelphia Phillies in July 1941. Soap operas followed in February 1947 (DuMont TV’s A Woman to Remember) and the first TV news helicopter was launched by KTLA Channel 5 in Los Angeles on 4 July 1958.

The first patent for color television was issued in Germany in 1904. Vladimir Kosma Zworykin, the Russia-born American innovator, came up with a complete color system in 1925. Baird himself demonstrated color TV transmission in 1928. Various researchers at Bell Laboratories perfected color television in the late 1920s. Georges Valenso of France patented a series of breakthrough technologies in 1938. But color TV became widespread only in the 1960s.

If you are one of the nearly 200 million American cell phone users, you probably signed a contract to get a steal of a deal on your phone. While this contract might be fine and dandy if you stay in the same town or city, travelers risk high roaming and per minute fees if they venture out of service area. This is where unlocking your cell phone comes into play. So how will you know if your phone is locked? And how do you unlock it if it is?

Cell phones providers AT&T/Cingular and T-Mobile are GSM (Group Special Mobile) and can technically be used worldwide if unlocked. Sprint, Nextel and Verizon are not GSM providers and cannot be unlocked. If you have a SIM chip in your phone, then it is GSM and you can perform a mobile unlock on your cell.

Once you’ve determined your phone number and account are tied to your SIM chip, not your actual phone, you can then perform the following test to see if your phone is locked:
? Borrow an activated SIM chip from a friend using a different wireless service provider
? Install the borrowed SIM chip in your phone and turn it on
? Try calling your friend’s phone number from a LAN or other mobile phone
? If it rings on your phone, it is unlocked.
? If your mobile with the borrowed SIM does not have service or issues an error message, your phone is locked.

Once you have determined your cell is locked, there are two basic techniques to perform a mobile unlock. You may have to try both of them to accomplish a mobile unlock.

Some phones may be unlocked by entering a code into it. The code is usually unique for your particular phone based on the IMEI (serial number) and provider. The phone’s IMEI is usually found in the battery case. Don’t confuse this number with the SIM number, they are separate. You can search online for an online “unlock code calculator”, then will enter your IMEI and phone model.

Other phones need software to “talk” to their operating system to unlock. You typically connect your phone to your PC, run a software program and flash your phones memory. We can sell you cables and software programs for your phone for a mobile unlock.

Sodium Vapour Lamp consists of a discharge tube made from a heat resistant glass, containing a small amount of metallic sodium, neon gas and two electrodes, Neon gas is added to start the discharge and to develop enough heat to vaporize the sodium. Because of law pressure inside the tube, a sufficiently long tube required to obtain more light. To reduce the overall dimension of the lamp, this tube is generally bent into U-shape.

The light produced by this lamp is yellowish which is produced at its optimum pressure of about 0.004mm of mercury. This pressure is obtained at a temperature of about 280° C and so it becomes necessary to maintain this temperature. For this purpose the U-tube is enclosed in a double walled flask to prevent lose of heat. The double walled flask is interchangeable and can be fitted on to another U-tube. While replacing the inner U-tube one must be very careful because if it is broken and sodium comes in contact with moisture, it may result in fire.

All electric discharge lamps require a higher voltage at the time of starting and low voltage during operation. Generally, sodium vapour lamps are operated by a high leakage reactance transformer. At starting a high voltage of about 450 volts is applied across the lamp which is sufficient to start the discharge. When the lamp is fully operative after 10 – 15 minutes, the voltage across it falls to about 150 volts. Because of the high reactance of circuit, the power factor is low and hence a p.f improvement capacitor is connected.

The efficiency of a low pressure sodium vapour lamp is very high (about 40 – 50 lumens/watt) and it produces a light of particular wavelength having yellow color. Sodium lamps are mainly employed for street, high way and airfield lighting where color distinction is not so necessary.