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Telecommunications stand for devices and systems that transmit electronic or optical signals across long distances. Telecommunications enables people around the world to contact one another, to access information instantly, and to communicate from remote areas. Telecommunications usually involves a sender of information and one or more recipients linked by a technology, such as a telephone system, that transmits information from one place to another. Telecommunications enables people to sand and receive personal messages across town, between countries, and to and from outer space. It also provides the key medium for delivering news, data, information, and entertainment.

Telecommunications devices convert different types of information, such as sound and video, into electronic or optical signals. Electronic signals typically travel along a medium such as copper wire or are carried over the air as radio waves. Optical signals typically travel along a medium such as strands of glass fibers. When a signal reaches its destination, the device on the receiving end converts the signal back into an understandable message, such as sound over a telephone, moving images on a television, or words and pictures on a computer screen.

Telecommunications messages can be sent in a variety of ways and by a wide range of devices. The messages can be seat from one sender to a single receiver (point-to-point) or from one sender to many receivers (point-to-multipoint). Personal communications, such as a telephone conversation between two people or a facsimile (fax) message (see Facsimile Transmission), usually involve point-to-point transmission. Point-to-multipoint telecommunications, often called broadcasts, provide the basis for commercial radio and television programming.

Telecommunications begin with messages that are converted into electronic or optical signals. Some signals, such as those that carry voice or music, are created in an analog or wave format, but may be converted into a digital or mathematical format for faster and more efficient transmission. The signals are then sent over a medium to a receiver, where they are decoded back into a form. that the person receiving the message can understand. There are a variety of ways to create and decode signals, and many different ways to transmit signals.

Individual people, businesses, and governments use many different types of telecommunications systems. Some systems, such as the telephone system, use a network of cables, wires, and switching stations for point-to-point communication. Other systems, such as radio and television, broadcast radio signals over the air that can be received by anyone who has a device to receive them. Some systems make use of several types of media to complete a transmission. For example, a telephone call may travel by means of copper wire, fiber-optic cable, and radio waves as the call is sent from sender to receiver. All telecommunications systems are constantly evolving as telecommunications technology improves. Many recent improvements, for example, offer high-speed broadband connections that are needed to send multimedia information over the Internet.

Personal computers have pushed the limits of the telephone system as more and more complex computer messages are being sent over telephone lines, and at rapidly increasing speeds. This need for speed has encouraged the development of digital transmission technology. The growing use of personal computers for telecommunications has increased the need for innovations in fiber-optic technology.

Telecommunications and information technologies are merging and converging. This means that many of the devices now associated with only one function may evolve into more versatile equipment. This convergence is already happening in various fields. Some telephones and pagers are able to store not only phone numbers but also names and personal information abo

A．Current development.

B．Transmission of message.

C．Computer networking.

D．Government regulation.

【8】

Griffith's film innovations had a direct effect on all of the following EXCEPT ______.

A．film editing

B．camera work

C．range of subjects

D．sound editing

Most people think of lions as strictly African beasts, but only because they've been killed off almost everywhere else. Ten thousand years ago lions spanned vast sections of the globe, and so did people, who —as they multiplied and organized —pat pressure on competitors at the top of the food chain. Now lions hold only a small fraction of their former habitat, and Asiatic lions, a subspecies that split from African lions perhaps 100,000 years ago, hang on to an almost impossibly small slice of their former domain.

India is the proud steward of these 300 or so lions, which live primarily in a 560-square-mile (1,450-square-kilometer) sanctuary. It took me a year and a half to get a permit to explore the entire Gir Forest —and no time at all to see why these lions became symbols of royalty and greatness. A tiger will slink through the forest unseen, but a lion stands its ground, curious and unafraid —lionhearted. Though they told me in subtle ways when I got too close, Gir's lions allowed me unique glimpses into their lives during my three months in the forest. It's odd to think that they are threatened by extinction; Gir has as many lions as it can hold —too many, in fact. With territory in short supply, lions prowl the periphery of the forest and even leave it altogether, often clashing with people. That's one reason India is creating a second sanctuary. There are other pressing reasons: outbreaks of disease or natural disasters. In 1994 canine distemper killed more than a third of Africa's Serengeti lions —thousand animals —a fate that could easily befall Gir's cats. These lions, saved by a prince at the turn of the 20th century, are especially vulnerable to disease because they descend from as few as a dozen individuals. "If you do a DNA fingerprint, Asiatic lions actually look like identical twins," says Stephen O'Brien, a geneticist who has studied them. Yet the perils are hidden, and you wouldn't suspect them by watching these lords of the forest. The lions exude vitality, and no small measure of charm.

Though the gentle intimacy of play vanishes when it's time to eat, meals in Git are not necessarily frenzied affairs. For a mother and cub sharing a deer, or a young male relishing an antelope, there's no need to fight for a cut of the kill. Prey animals are generally smaller in Gir than they are in Africa, and hunting groups tend to be smaller as well. The lions themselves aren't as big as African lions, and they have shorter manes and a long fold of skin on their undersides that many lions in Africa don't have.

What impressed the author most when he went to watch the lions in the Gir Forest?

A．The lions were on the brink of extinction.

B．They were suffering from a fatal disease.

C．They allowed him to see their vitality and charm at close quarters.

D．Mother lion and her cub shared a deer.