电子与通信工程硕士专业英语part 6

Ongoing Developments
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading： preface
Telecommunications are the transmission of words, sounds, images, or data in the form of electronic or electromagnetic signals or impulses. Transmission media include the telephone (using wire or optical cable), radio, television, microwave, and satellite. Data communication, the fastest growing field of telecommunication, is the process of transmitting data in digital form by wire or radio.
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading：
Applications · Host-Terminal In these types of communications, one computer—the host computer—is connected to one or more terminals. Each terminal transmits data to or receives data from the host computer. For example, many airlines have terminals that are located at the desks of ticket agents and connected to a central, host computer. These terminals obtain flight information from the host computer, which may be located hundreds of kilometers away from the agent’s site. ……
Applications
·File-Transfer ·Computer-Network
Lesson 3 电 信 Telecommunications
• 内容大纲 Outline：
·Network Telecommunication Services ·Information Retrieval ·Electronic Mail ·Bulletin Board
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading：
Applications · Computer-Network …… The three kinds of computer networks are local area networks (LAN), private branch exchange (PBX) networks, and wide-area networks (WAN). LANs interconnect devices with a group of cables; the devices communicate at a high speed and must be in close proximity.
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading：
Hardware and Software Each telecommunications device uses hardware, which connects a device to the transmission line; and software, which makes it possible for a device to transmit information through the line. · Hardware Hardware usually consists of a transmitter and a cable interface, or if the telephone is used as a transmission line, a modulator/ demodulator, or modem.
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading： preface
The devices used can be computers, terminals (devices that transmit and receive information), and peripheral equipment such as printers. The transmission line used can be a normal or a specially purchased telephone line called a leased, or private line. It can also take the form of a microwave or a communications-satellite linkage, or some combination of these various systems.
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading：
Hardware and Software …… A cable interface, as the name indicates, connects a device to a cable. It converts the transmitted signals from the form required by the device to the form required by the cable. ……
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading：
Hardware and Software · Software Among the different kinds of software are file-transfer, host and network programs. File-transfer software is used to transmit a data file from one device to another. Host software identifies a host computer as such and controls the flow of data among devices connected to it. Network software allows devices in a computer network to transmit information to one another.
• 技术背景 Background：
Lesson 3 电 信 Telecommunications
Lesson 3 电 信 Telecommunications
• 内容大纲 Outline：
Hardware and Software ·Hardware ·Software
·Host-Terminal
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading：
Applications · File-Transfer …… An outgrowth of file transfer is electronic mail. For example, an employee might write a document such as a letter, memorandum, or report on a computer and then send the document to another employee’s computer.
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading：Fra Baidu bibliotek
Applications A PBX network interconnects devices with a telephone switching system; in this kind of network, the devices must again be in close proximity. In wide-area networks, on the other hand, the devices can be at great distances from one another, and such networks usually inter-connect devices by means of telephone.
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading：
Telecommunication Services · Network A public network service leases time on a WAN, thereby providing terminals in other cities with access to a host computer. Examples of such services include Telenet, Tymnet, Uninet, and Datapac. These services sell the computing power of the host computer to users who cannot or do not wish to invest in the purchase of such equipment.
Lesson 3 电 信 Telecommunications
(UNIT 8 Passage B ) Intensive reading：1. 2.
• 技术背景 Background：
Lesson 3 电 信 Telecommunications
The four phases of the evolution of communications networks are shown in Table 8.1——
Lesson 3 电 信 Telecommunications
精读详解 Intensive reading： preface
Digital data can be generated directly in a 1/0 binary code by a computer or can be produced from a voice or visual signal by a process called encoding. A data communications network is created by interconnecting a large number of information sources so that data can flow freely among them. The data may consist of a specific item of information, a group of such items, or computer instructions. Example include a news item, a bank transaction, a mailing address, a letter, a book, a mailing list, a bank statement, or a computer program.