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T.V.ENGINEERING TEXT BOOK BY R.R GULATI

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Development of Television

Television* means ‘to see from a distance’. The desire in man to do so has been there for ages.
In the early years of the twentieth century many scientists experimented with the idea of
using selenium photosensitive cells for converting light from pictures into electrical signals
and transmitting them through wires.

The first demonstration of actual television was given by J.L. Baird in UK and C.F.
Jenkins in USA around 1927 by using the technique of mechanical scanning employing rotating
discs. However, the real breakthrough occurred with the invention of the cathode ray tube and
the success of V.K. Zworykin of the USA in perfecting the first camera tube (the iconoscope)
based on the storage principle. By 1930 electromagnetic scanning of both camera and picture
tubes and other ancillary circuits such as for beam deflection, video amplification, etc. were
developed. Though television broadcast started in 1935, world political developments and the
second world war slowed down the progress of television. With the end of the war, television
rapidly grew into a popular medium for dispersion of news and mass entertainment.

Television Systems

At the outset, in the absence of any international standards, three monochrome (i.e. black and
white) systems grew independently. These are the 525 line American, the 625 line European
and the 819 line French systems. This naturally prevents direct exchange of programme between
countries using different television standards. Later, efforts by the all world committee on
radio and television (CCIR) for changing to a common 625 line system by all concerned proved
ineffective and thus all the three systems have apparently come to stay. The inability to change
over to a common system is mainly due to the high cost of replacing both the transmitting
equipment and the millions of receivers already in use. However the UK, where initially a 415
line monochrome system was in use, has changed to the 625 line system with some modification
in the channel bandwidth. In India, where television transmission started in 1959, the 625-B
monochrome system has been adopted.

The three different standards of black and white television have resulted in the
development of three different systems of colour television, respectively compatible with the
three monochrome systems. The original colour system was that adopted by the USA in 1953
on the recommendations of its National Television Systems Committee and hence called the
NTSC system. The other two colour systems–PAL and SECAM are later modifications of the
NTSC system, with minor improvements, to conform to the other two monochrome standards.

EMBEDDED SYSTEMS TEXTBOOK - BY SHIBU Kv Pdf

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• CLICK HERE Embedded Systems Textbook By Raj Kamal

• CLICK HERE Antenna and Wave Propagation Textbook 

•  CLICK HERE T.V.Engineering Textbook by R.R.Gulati

An Embedded System is a combination of computer hardware and software, and perhaps additional mechanical or other parts, designed to perform a specific function. A good example is the microwave oven. Almost every household has one, and tens of millions of them are used everyday, but very few people realize that a processor and software are involved in the preparation of their lunch or dinner.

                       This is in direct contrast to the personal computer in the family room. It too is comprised of computer hardware and software and mechanical components (disk drives, for example). However, a personal computer is not designed to perform a specific function rather; it is able to do many different things. Many people use the term general-purpose computer to make this distinction clear. As shipped, a general-purpose computer is a blank slate; the manufacturer does not know what the customer will do wish it. One customer may use it for a network file server another may use it exclusively for playing games, and a third may use it to write the next great American novel.

                     Frequently, an embedded system is a component within some larger system. For example, modern cars and trucks contain many embedded systems. One embedded system controls the anti-lock brakes, other monitors and controls the vehicle’s emissions, and a third displays information on the dashboard. In some cases, these embedded systems are connected by some sort of a communication network, but that is certainly not a requirement.

                           At the possible risk of confusing you, it is important to point out that a general-purpose computer is itself made up of numerous embedded systems. For example, my computer consists of a keyboard, mouse, video card, modem, hard drive, floppy drive, and sound card-each of  which is an embedded system. Each of these devices contains a processor and software and is designed to perform a specific function. For example, the modem is designed to send and receive digital data over analog telephone line. That’s it and all of the other devices can be summarized in a single sentence as well.

              If an embedded system is designed well, the existence of the processor and software could be completely unnoticed by the user of the device. Such is the case for a microwave oven, VCR, or alarm clock. In some cases, it would even be possible to build an equivalent device that does not contain the processor and software. This could be done by replacing the combination with a custom integrated circuit that performs the same functions in hardware. However, a lot of flexibility is lost when a design is hard-cooled in this way. It is mush easier, and cheaper, to change a few lines of software than to redesign a piece of custom hardware.

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COMPUTER NETWORKS BY - A Tanenbaum

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