Digital Switchover

In February of 2009, all the analog TV stations will stop broadcasting their analog signals. They will switch over to digital signals. Which brings up two questions. What is the difference between an analog and digital signal? And why is digital better?

Analog signals have been around in telephones, radios and TVs for decades. They use changing voltage levels to send information. In a telephone or a radio station, the sound of someone's voice is converted to a changing voltage by a microphone. In a TV camera, light levels are sent out as changing voltages.

With digital signals, you don't use changing voltages. Instead, the information is converted into numbers and the numbers are sent. There are two big advantages to sending numbers. First, interference has almost no effect on numbers. Second, you can apply mathematical formulas to the numbers to compress them. In other words, you can fit more information into less space with digital signals. So, you can fit more stations onto a cable system, or send several shows at once from a single TV station.

Some folks will get a sneak preview of what's going to happen during the digital switchover when Wilmington, NC tries it out on September 8, 2008, in a digital-TV market test.