Television

European colour television was developed somewhat later and was hindered by a continuing division on technical standards. Having decided to adopt a higher-definition 625-line system for monochrome transmissions, with a lower frame rate but with a higher overall bandwidth, Europeans could not directly adopt the U.S. colour standard. This was widely perceived as inadequate anyway because of its hue error problems, which became particularly acute with the introduction of videotape recorders in the late 1950s. There was also less urgency, since there were fewer commercial motivations, European television broadcasters being predominantly state-owned at the time.

As a consequence, although work on various colour encoding systems started already in the 1950s, with the first SECAM patent being registered in 1956, many years had passed when the first broadcasts actually started in 1967. Unsatisfied with the performance of NTSC and of initial SECAM implementations, the Germans unveiled PAL (phase alternating line) in 1963, technically similar to NTSC but borrowing some ideas from SECAM. The French continued with SECAM, notably involving Russians in the development.

UNIT 13

Cell phone

Digital cell phones are the second generation (2G) of cellular technology. They use the same radio technology as analog phones, but they use it in a different way. Analog systems do not fully utilize the signal between the phone and the cellular network -- analog signals cannot be compressed and manipulated as easily as a true digital signal. This is the reason why many cable companies are switching to digital -- so they can fit more channels within a given bandwidth. It is amazing how much more efficient digital systems can be.

Digital phones convert your voice into binary information (1s and 0s) and then compress it. This compression allows between three and 10 digital cell-phone calls to occupy the space of a single analog call.

Many digital cellular systems rely on frequency-shift keying (FSK) to send data back and forth over AMPS. FSK uses two frequencies, one for 1s and the other for 0s, alternating rapidly between the two to send digital information between the cell tower and the phone. Clever modulation and encoding schemes are required to convert the analog information to digital, compress it and convert it back again while maintaining an acceptable level of voice quality. All of this means that digital cell phones have to contain a lot of processing power.

UNIT 14

Computers

0 and 1. Those two small numbers changed our world. Computers, data communication, the Internet understand only two numbers, 0 and 1. Digital electronics based on Boolean algebra that represents the numbers to the base of two. Since 1970 until today the digital ICs have been in constant development. Everywhere we hear about new microprocessors, which are quicker, more complex, smarter and less expensive than the previous one. We can state that ever since the first computers electronics improved it self. The calculation became simpler. The measurement equipment becomes more accurate. In conclusion, I can say that the science of electronics is one of most important sciences today. We all witness the influence of electronics on our life in good and bad side as well. The process of development was relatively quick and interesting. The best brains of 20th century were the head of this process. But the history of electronics has not ended, as we see, and our using of electronics is the best evidence for it.

UNIT 15