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UNIT 1 Microelectronics and Electronic Circuits1-1Introduction to Microelectronics首先学习KEY WORDS.学习课文英文翻译成中文，并注意学习专业词汇。
Para. 1对太空的探索以及人造地球卫星的发展，增强了人们对减少电子电路的重量和体积的重要性的认识。
另外，即使电流在计算机中流得相当快，但是由于电子元器件之间的互联所导致的信号的时间延迟是不能不考虑的。
如果这种互联在尺寸上能减小，无疑会使计算机的运行速度更快。
Para. 2微电子学主要是使常规电路微型化。
比如一个运算放大器，包括许多彼此互连的分立器件，有二极管，电阻，象这样一个完整的电路，可以制作在一个很小的基片上。
这个完整的微型化的电路就称之为集成电路（IC）。
Para. 3IC体积小，重量轻，坚固耐用，稳定可靠。
它们比同等宏观电路（分立元件电路）需要更少的功耗和更低的电压。
因此，它们可以工作在更低的温度下，而在这种温度下，分立器件可能都不能正常工作，因为温度没有达到正常工作温度范围。
相应地，几乎不会产生寄生电容和延时，因为在IC中，器件之间地互联非常短。
维护起来跟简单，因为，如果在一个IC里边地器件坏了，通常用一个新的IC来替换坏的。
表面技术的大规模生产技术已经降低了许多IC的成本，因此，它们就跟单个晶体管一样便宜。
最后的结果就是，大部分常用的分立器件电路被IC所取代。
Para. 4有两种基本类型的IC：一种是独立IC,一种是薄或厚的膜状IC. 独立IC是构建在单个的半导体晶体的基片里边，通常用的是硅。
薄或厚的膜状IC是形成在一种绝缘材料的表面，像玻璃或者陶器。
还有一种混合的IC所包含的不仅仅是单个的基片。
在这里，这个词“混合”同样也指独立IC和薄或厚的膜状IC结合体。
Para. 5也可根据其功能不同对集成电路进行分类。
数字IC（也称为逻辑IC）通常用作开关，表示接通或关闭。
英语原文：Life of LED-Based White Light SourcesThe interest for using light-emitting diodes (LEDs) for display and illumination applications has been growing steadily over the past few years. The potential for long life and reduced energy use are two key attributes of this rapidly evolving technology that have generated so much interest for its use in the above mentioned applications. Traditionally, the lamp life of light sources commonly used in illumination applications is determined by subjecting them to a predetermined on/off cycle until half the number of light sources cease to produce light. Unlike these sources, LEDs rarely fail catastrophically; instead, their light output slowly degrades over time. Even if an LED is technically operating and producing light, at some point the amount of light produced by the LED will be insufficient for the intended application. Therefore, the life of an LED should be based on the amount of time that the device can produce sufficient light for the intended application,rather than complete failure. Based on this argument, a recent publication from an industry group defines the life of an LED device or system for use in general lighting applications as the operating time, in hours, for the light output to reach 70% of its initial value.The most widely used white LEDs incorporate a layer of phosphor over a GaN-based, short-wavelength light emitter. Usually, the phosphor is embedded inside an epoxy resin that surrounds the LED die. Some portion of the short-wavelength radiation emitted by the LED is down-converted by the phosphor, and the combined radiation creates white light.Early white LEDs were packaged similar to the indicator-style colored LEDs, specifically 5 mm and SMD (surface mount devices). Although these products demonstrated the concept of a white light source, they did not produce sufficient light for display and illumination applications. Furthermore, these indicator-style white LEDs had a relatively short life, 5000–10 000h to reach 70% light level under normal operating conditions. To address the higher luminous flux requirements, manufacturers have started to commercialize high-power illuminator LEDs that are presently producing over one hundred times the flux compared to indicator-style white LEDs. The higher light output isachieved by using larger dies, higher drive currents,and improved heat extraction methods. In addition,some manufacturers are using better encapsulants to improve the life of white LEDs.There are several studies that have investigated the aging mechanisms of GaN-based LEDs. During the 1990s,Barton et al. investigated the degradation of GaN-based blue LEDs and showed that light output reduction over time occurred primarily due to the yellowing of the epoxy surrounding the die. In 2001, Narendran et al. observed that indicator-style white LED packages degraded very rapidly, with the LEDs reaching the 50% light output level within 6000 h. In that same study, it was shown that the chromaticity values of the white LEDs shifted toward yellow over time, and it was speculated that the yellowing of the epoxy was the main cause for light output degradation. Therefore, based on past studies,the primary reason for the degradation of indicator-style white LED packages is the yellowing of the epoxy that is caused by excessive heat at the p-n-junction of the LED. Some of the newer illuminator-style white LEDs use encapsulant materials that have lower photodegradation characteristics,and therefore have a lower degradation rate. However, there are factors such as the degradation of the die attaché epoxy, discoloration of the metal reflectors and the lead wires, and degradation of the semiconducting element that are influenced by heat, and these all contribute to the overall degradation of the white LED. Although the newer high-power white LEDs would have a lower degradation rate compared to the early indicator-style devices, it is the heat at the p-n-junction that most influences the degradation. The heat at the p-n-junction is caused by the ambient temperature and the ohmic heating at the bandgap.As stated earlier, long life is one key feature of LED technology that has attracted so many end-use communities. To benefit from the long-life feature, it is the final system that has to operate for a long time, not just the individual LED. As noted in past studies, heat at the p-n-junction is one of the key factors that determine the life of the white LED. Therefore, if systems are not properly designed with good thermal managemen techniques, even if they use long-life white LEDs the life of the final system would be short. Developing the relationship between junction temperature and life would be very usefulfor producing long-life systems.Although there are different methods available for estimating the junction temperature of LEDs, they are not very convenient,especially once the LEDs are integrated into a system . Furthermore, these methods are not direct; consequently, they are prone to erroneous results. Alternatively, it is much more convenient and direct to measure the heat at a location external to the LED package that is sufficiently close to the junction and where a temperature sensor can be directly attached. The temperature of this point should have a good relationship to the junction temperature. The point where a temperature sensor can be attached for this measurement could be the lead wire (cathode side) for the indicator-style LEDs and the board for high-power LEDs. Most manufacturers can recommend such a point,and we refer to this as the T-point in this manuscript.Since white LEDs in the marketplace are packaged differently, their ability to transfer heat from the die to the surrounding environment is different from product to product. Therefore, it is reasonable to assume that different products have different degradation rates as a function of heat. A graph that shows the life of the LED as a function of T-point temperature is extremely useful for system manufacturers to build reliable, long-lasting systems. By knowing how much impact heat has on the degradation rate or life of the LED, the system manufacturer can select components and drive parameters, including the amount of heat sink and drive current, for a product being designed for a given application.Therefore, the objective of the study presented in this manuscript was to investigate the relationship between the T-point temperature and life of a white LED. A second objective was to understand the degradation rate of different high-power white LED products presently available in the marketplace.To understand the relationship between the T-point temperature and life, one type of high-power white LED that is commonly available in the marketplace was selected. Several of these LEDs were subjected to a life test under different ambient temperatures. The details of the experimental setup are described in the following paragraphs.Because the different LED arrays have to operate at a particular ambient temperature, the arrays were placed inside specially designed, individual life-test chambers. The test chambers had two different functions: 1) to keep the ambient temperature constant for the LED arrays and 2) to act as light-integrating boxes for measuring light output. Each individual LED array was mounted at the center of the inside top surface of a life-test chamber. A photodiode attached to the center of the left panel continuously measured the light output.A small white baffle placed over the photodiode shielded it from the direct light, allowing only the reflected light to reach the photodiode. A resistance temperature detector placed on top of the baffle measured the chamber’s ambient temperature and controlled the heater that provided the necessary heat to the chamber through a temperature controller. The temperature in-side the box remained within ±1℃.The heater was attached to a raised aluminum plate with a matte-white cover that sat on the chamber floor. The temperature was estimated using a J-type thin wire thermocouple soldered to the T-point of white LED. For each chamber, an external LED driver controlled the current flow through the LEDs. All life-test were placed inside a temperature-controlled room. The life-test chambers were staggered vertically and horizontally to ensure that heat rising from the bottom chambers did not affect the chambers above them.The results of this study underscore the importance of packaging white LEDs using proper thermal management to maintain light output, and thereby extend system life. Heat at the p-n-junction is one of the main factors that affect the life of white LEDs. Therefore, knowing the relationship between life and heat would be very useful for manufacturers who are interested in developing reliable, long-lasting systems.Results from the first experiment—conducted under various ambient temperatures to understand the relationship between T-point temperature and life—indicate that life decreases with increasing temperature in an exponential manner. Results from the second experiment—conducted to understand how different commercial white LEDs perform under identical operating conditions—show a large variation in life among the different packages, indicating that the packages used different heat extraction techniques and materials.As part of ongoing research, we hope to further investigate how the different commercial LEDs are affected by heat and finally develop a family of curves that illustrate the relationship between life and T-point temperature for the different products.中文翻译：基于LED的白色光源的寿命在过去几年中利用发光二极管(led)显示和作为照明应用的技术一直在稳步增长。
电子信息工程电路编程中的AT89C51单片机译文标题电路编程中的AT89C51单片机AT89C51 In-Circuit Programming 原文标题作者Robert W.Sparks等译名国籍美国斯帕克等W.罗伯特Atmel Corporation原文出处摘要本应用说明的是ATMEL公司AT89C51的电路可编程闪存的微控制器。
为在电路可编程AT89C51的应用提出了与应用程序相关的例子，它的修改要求支持在线编程。
这种方法显示在该应用程序中的AT89C51单片机可通过商业电话线远程改编。
本应用笔记中描述的电路，仅支持5伏电压下编程，需要使用一个AT89C51-XX-5。
标准A T89C51的需要12伏电压。
该应用程序的软件可从ATMEL下载。
总论当不在进行程序设计的时候，在电路设计中的AT89C51设计将变得透明化。
在编程期间必须重视EA/VPP这一脚。
在不使用外部程序存储器的应用程序中，这脚可能会永久接到VCC。
应用程序使用的外部程序存储器要求这一脚为低电平才能正常运行。
RST在编程期间必须为高电平。
应该提供一种方法使得电路通入电源以后，使RST代替主要的复位电路起到复位的作用。
在编程过程中，PSEN必须保持低电平，在正常运行期间绝不能使用。
ALE/ PRO在编程过程中输出低电平，在正常运行期间绝不能使用在编程过程中AT89C5I / 端口是用于模式应用程序，地址和数据选择的，可能要该控制器从应用的电路隔离。
如何做到这一点取决于应用程序输入端在编程过程中，控制器必须与应用电路的信号来源隔离。
带有三个输出状态的缓冲区在应用程序之间插入电路和控制器，同时在编程时缓冲区输出三种状态。
一个多路复用器用于信号源之间进行选择，适用于任何一方的应用电路或编程控制器电路的信号输出端如果应用的电路可以允许端口在编程过程中的状态变化，则不需要改变电路。
如果应电路的状态，必须事先在编程过程中的保持不变，可能在控制器和应用电路中插入锁存。
电子信息工程专业英语写作范文In the realm of electronic information engineering, the art of writing is as crucial as the circuitry itself. It serves as the bridge connecting complex ideas with practical applications.The field demands a clear and concise writing style, ensuring that technical specifications are communicated without ambiguity. Precision is key; a single misplaced word can lead to significant misunderstandings in project implementation.As we delve into the intricacies of electronic systems, writing becomes a tool for documenting research, detailing methodologies, and articulating innovative solutions. It is through well-structured essays that we can convey the subtleties of our work to both peers and laypersons.In crafting an English composition for this discipline, one must consider the audience's technical background. For fellow engineers, the language can be dense with jargon, whereas for a general audience, explanations must be simplified without sacrificing accuracy.The evolution of electronic information engineering is a testament to the power of written communication. From the early days of vacuum tubes to the sophisticated microchips of today, each breakthrough has been documented and sharedthrough the written word.A well-written report not only informs but also inspires. It can ignite the imagination of students, guide the research of professionals, and even influence policy decisions in the tech industry.The future of our discipline hinges on our ability to articulate our ideas effectively. As we continue to push the boundaries of what is possible, our writing must evolve to match the complexity and innovation of our work.In conclusion, the role of English writing in electronic information engineering is multifaceted. It is a means of communication, a tool for documentation, and a catalyst for progress. As we refine our craft, we contribute to the ongoing dialogue that shapes the technological landscape.。
电子信息工程作文英文翻译下载温馨提示:该文档是我店铺精心编制而成，希望大家下载以后，能够帮助大家解决实际的问题。
文档下载后可定制随意修改，请根据实际需要进行相应的调整和使用，谢谢!并且，本店铺为大家提供各种各样类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，如想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by theeditor. I hope that after you download them,they can help yousolve practical problems. The document can be customized andmodified after downloading,please adjust and use it according toactual needs, thank you!In addition, our shop provides you with various types ofpractical materials,such as educational essays, diaryappreciation,sentence excerpts,ancient poems,classic articles,topic composition,work summary,word parsing,copyexcerpts,other materials and so on,want to know different data formats andwriting methods,please pay attention!Electronic Information Engineering。
1.As data networks advanced…also grew more complex.由于数据网络从面向终端的系统向分组交换、计算机与计算机连接的方向发展, 执行网络功能所必需的协议也变得愈来愈复杂。
2.An additional bit called a parity bit…during transmission.在每个字符的后面有时还包括一个称为奇偶校验位的附加位, 它们测试数据位在传输过程中是否被意外改变。
3.As already stated, with…downlink（FDD paired bands）.如前所述, 在非对称通信量应用中, TD-SCDMA利用可用频谱的效率比其他3G标准高, 因为它在只利用一个频带（TDD单一频带）而不是两个独立的频带（FDD成对频带）进行上行与下行通信。
4.Although often simpler to implement, …digital modulation.虽然光纤系统的模拟调制易于实现, 但其效率较低, 且要求在接收端有比数字调制高得多的信噪比。
5.At present, the bandwidth…electronics （）is possible.目前传输100km的几吉赫兹的调制信号和传输300km的几百兆赫兹的调制信号都是可能的, 因此光纤系统的可用带宽并没有得到充分利用。
6.Both TD-SCDMA deployments-TSD…unpaired bands awarded.TD-SCDMA的两种部署——TSM和TDDCLR的数据速率、频谱利用率、覆盖率、移动性和可靠性等性能是一样的, 并基本上为所有取得非成对TDD频段牌照的运营商所采用。
7.Crossbar sw itching was carried…selection for all calls.纵横制交换由一个称为标志器的特定电路控制, 标志器提供整个号码的公共控制并选择所有呼叫的路由。
本科毕业设计（论文）中英文对照翻译院(系部）电气工程与自动化专业名称电子信息工程年级班级 04级7班学生姓名指导老师Infrared Remote Control SystemAbstractRed outside data correspondence the technique be currently within the scope of world drive extensive usage of a kind of wireless conjunction technique，drive numerous hardware and software platform support。
Red outside the transceiver product have cost low，small scaled turn，the baud rate be quick, point to point SSL, be free from electromagnetism thousand Raos etc。
characteristics, can realization information at dissimilarity of the product fast, convenience, safely exchange and transmission，at short distance wireless deliver aspect to own very obvious of advantage。
Along with red outside the data deliver a technique more and more mature，the cost descend，red outside the transceiver necessarily will get at the short distance communication realm more extensive of application。
外文原文：Database Management Systems A database (sometimes spelled data base) is also called an electronic database , referring to any collection of data, or information, that is specially organized for rapid search and retrieval by a computer. Databases are structured to facilitate the storage, retrieval , modification, and deletion of data in conjunction with various data-processing operations .Databases can be stored on magnetic disk or tape, optical disk, or some other secondary storage device. A database consists of a file or a set of files. The information in these files may be broken down into records, each of which consists of one or more fields. Fields are the basic units of data storage , and each field typically contains information pertaining to one aspect or attribute of the entity described by the database . Using keywords and various sorting commands, users can rapidly search , rearrange, group, and select the fields in many records to retrieve or create reports on particular aggregate of data. Complex data relationships and linkages may be found in all but the simplest databases .The system software package that handles the difficult tasks associated with creating ,accessing, and maintaining database records is called a database management system(DBMS).The programs in a DBMS package establish an interface between the database itself and the users of the database.. (These users may be applications programmers, managers and others with information needs, and various OS programs.) A DBMS can organize, process, and present selected data elements form the database. This capability enables decision makers to search, probe, and query database contents in order to extract answers to nonrecurring and unplanned questions that aren’t available in regular reports. These questions might initially be vague and/or poorly defined ,but people can “browse” through the database until they have the needed information. In short, the DBMS will “manage” the stored data items and assemble the needed items from the common database in response to the queries of those who aren’t programmers.A database management system (DBMS) is composed of three major parts:(1)a storage subsystem that stores and retrieves data in files;(2) a modeling 7and manipulation subsystem that provides the means with which to organize the dataand to add , delete, maintain, and update the data;(3)and an interface between the DBMS and its users. Several major trends are emerging that enhance the value and usefulness of database management systems; Managers: who require more up-to-data information to make effective decision Customers: who demand increasingly sophisticated information services and more current information about the status of their orders, invoices, and accounts. Users: who find that they can develop custom applications with database systems in a fraction of the time it takes to use traditional programming languages. Organizations : that discover information has a strategic value; they utilize their database systems to gain an edge over their competitors. The Database Model A data model describes a way to structure and manipulate the data in a database. The structural part of the model specifies how data should be represented(such as tree, tables, and so on ).The manipulative part of the model specifies the operation with which to add, delete, display, maintain, print, search, select, sort and update the data. Hierarchical Model The first database management systems used a hierarchical model-that is-they arranged records into a tree structure. Some records are root records and all others have unique parent records. The structure of the tree is designed to reflect the order in which the data will be used that is ,the record at the root of a tree will be accessed first, then records one level below the root ,and so on. The hierarchical model was developed because hierarchical relationships are commonly found in business applications. As you have known, an organization char often describes a hierarchical relationship: top management is at the highest level, middle management at lower levels, and operational employees at the lowest levels. Note that within a strict hierarchy, each level of management may have many employees or levels of employees beneath it, but each employee has only one manager. Hierarchical data are characterized by this one-to-many relationship among data. In the hierarchical approach, each relationship must be explicitly defined when the database is created. Each record in a hierarchical database can contain 8only one key field and only one relationship is allowed between any two fields. This can create a problem because data do not always conform to such a strict hierarchy. Relational Model A major breakthrough in database research occurred in 1970 whenE. F. Codd proposed a fundamentally different approach to database management called relational model ,which uses a table as its data structure. The relational database is the most widely used database structure. Data is organized into related tables. Each table is made up of rows called and columns called fields. Each record contains fields of data about some specific item. For example, in a table containing information on employees, a recordwould contain fields of data such as a person’s last name ,first name ,and street address. Structured query language(SQL)is a query language for manipulating data in a relational database .It is nonprocedural or declarative, in which the user need only specify an English-like description that specifies the operation and the described record or combination of records. A query optimizer translates the description into a procedure to perform the database manipulation. Network Model The network model creates relationships among data through a linked-list structure in which subordinate records can be linked to more than one parent record. This approach combines records with links, which are called pointers. The pointers are addresses that indicate the location of a record. With the network approach, a subordinate record can be linked to a key record and at the same time itself be a key record linked to other sets of subordinate records. The network mode historically has had a performance advantage over other database models. Today , such performance characteristics are only important in high-volume ,high-speed transaction processing such as automatic teller machine networks or airline reservation system. Both hierarchical and network databases are application specific. If a new application is developed ,maintaining the consistency of databases in different applications can be very difficult. For example, suppose a new pension application is developed .The data are the same, but a new database must be created. Object Model The newest approach to database management uses an object model , in which records are represented 9by entities called objects that can both store data and provide methods or procedures to perform specific tasks. The query language used for the object model is the same object-oriented programming language used to develop the database application .This can create problems because there is no simple , uniform query language such asSQL . The object model is relatively new, and only a few examples of object-oriented database exist. It has attracted attention because developers who choose an object-oriented programming language want a database based on an object-oriented model. Distributed Database Similarly , a distributed database is one in which different parts of the database reside on physically separated computers . One goal of distributed databases is the access of information without regard to where the data might be stored. Keeping in mind that once the users and their data are separated , the communication and networking concepts come into play . Distributed databases require software that resides partially in the larger computer. This software bridges the gap between personal and large computers and resolves the problems of incompatible data formats. Ideally, it would make the mainframe databases appear to be large libraries of information, with most of the processing accomplished on the personal computer. A drawback to some distributed systems is that they are often based on what is called a mainframe-entire model , in which the larger host computer is seen as the master and the terminal or personal computer is seen as a slave. There are some advantages to this approach . With databases under centralized control , many of the problems of data integrity that we mentioned earlier are solved . But today’s personal computers, departmental computers, and distributed processing require computers and their applications to communicate with each other on a more equal or peer-to-peer basis. In a database, the client/server model provides the framework for distributing databases. One way to take advantage of many connected computers running database applications is to distribute the application into cooperating parts that are independent of one anther. A client is an end user or computer program that requests resources across a network. A server is a computer running 10software that fulfills those requests across a network . When the resources are data in a database ,the client/server model provides the framework for distributing database.A file serve is software that provides access to files across a network. A dedicated file server is a single computer dedicated to being a file server. This is useful ,for example ,if the files are large and require fast access .In such cases, a minicomputer or mainframe would be used as a file server. A distributed file server spreads the filesaround on individual computers instead of placing them on one dedicated computer. Advantages of the latter server include the ability to store and retrieve files on other computers and the elimination of duplicate files on each computer. A major disadvantage , however, is that individual read/write requests are being moved across the network and problems can arise when updating files. Suppose a user requests a record from a file and changes it while another user requests the same record and changes it too. The solution to this problems called record locking, which means that the first request makes others requests wait until the first request is satisfied . Other users may be able to read the record, but they will not be able to change it . A database server is software that services requests to a database across a network. For example, suppose a user types in a query for data on his or her personal computer . If the application is designed with the client/server model in mind ,the query language part on the personal computer simple sends the query across the network to the database server and requests to be notified when the data are found. Examples of distributed database systems can be found in the engineering world. Sun’s Network Filing System(NFS),for example, is used in computer-aided engineering applications to distribute data among the hard disks in a network of Sun workstation. Distributing databases is an evolutionary step because it is logical that data should exist at the location where they are being used . Departmental computers within a large corporation ,for example, should have data reside locally , yet those data should be accessible by authorized corporate management when they want to consolidate departmental data . DBMS software will protect the security and integrity 11of the database , and the distributed database will appear to its users as no different from the non-distributed database . In this information age, the data server has become the heart of a company. This one piece of software controls the rhythm of most organizations and is used to pump information lifeblood through the arteries of the network. Because of the critical nature of this application, the data server is also the one of the most popular targets for hackers. If a hacker owns this application, he can cause the company’s "heart" to suffer a fatal arrest. Ironically,although most users are now aware of hackers, they still do not realize how susceptible their database servers are to hack attacks. Thus, this article presents a description of the primary methods of attacking database servers (also known as SQL servers) and shows you how to protect yourself from these attacks. You should note this information is not new. Many technical white papers go into great detail about how to perform SQL attacks, and numerous vulnerabilities have been posted to security lists that describe exactly how certain database applications can be exploited. This article was written for the curious non-SQL experts who do not care to know the details, and as a review to those who do use SQL regularly. What Is a SQL Server?A database application is a program that provides clients with access to data. There are many variations of this type of application, ranging from the expensive enterprise-level Microsoft SQL Server to the free and open source mySQL. Regardless of the flavor, most database server applications have several things in common. First, database applications use the same general programming language known as SQL, or Structured Query Language. This language, also known as a fourth-level language due to its simplistic syntax, is at the core of how a client communicates its requests to the server. Using SQL in its simplest form, a programmer can select, add, update, and delete information in a database. However, SQL can also be used to create and design entire databases, perform various functions on the returned information, and even execute other programs. To illustrate how SQL can be used, the following is an example of a simple standard SQL query anda more powerful SQL query: 12 Simple: "Select * fromdbFurniture.tblChair" This returns all information in the table tblChair from the database dbFurniture.Complex: "EXEC master..xp_cmdshell ‘dir c:\’" This short SQL command returns to the client the list of files and folders under the c:\ directory of the SQL server. Note that this example uses an extended stored procedure that is exclusive to MS SQL Server. The second function that database server applications share is that they all require some form of authenticated connection between client and host. Although the SQL language is fairly easy to use, at least in its basic form,any client that wants to perform queries must first provide some form of credentials that will authorize the client; the client also must define the format of the request and response. This connection is defined by several attributes, depending on the relative location of the client and what operating systems are in use. We could spend a whole article discussing various technologies such as DSN connections, DSN-less connections, RDO, ADO, and more, but these subjects are outside the scope of this article. If you want t o learn more about them, a little Google’ing will provide you with more than enough information. However, the following is a list of the more common items included in a connection request. Database source Request type Database User ID Password Before any connection can be made, the client must define what type of database server it is connecting to. This is handled by a software component that provides the client with the instructions needed to create the request in the correct format. In addition to the type of database, the request type can be used to further define how the client’s request will be handled by the server. Next comes the database name and finally the authentication information. All the connection information is important, but by far the weakest link is the authentication information—or lack thereof. In a properly managed server, each database has its own users with specifically designated permissions that control what type of activity they can perform. For example, a user account would be set up as read only for applications that need to only access information. Another account should be used for inserts or updates, and maybe even a third 13account would be used for deletes. This type of account control ensures that any compromised account is limited in functionality. Unfortunately, many database programs are set up with null or easy passwords, which leads to successful hack attacks。
毕业设计(论文)外文资料翻译系别：信息专业：电子信息工程班级： 081姓名：学号：附件：1.外文资料翻译译文；2外文原文指导教师评语：签名：年月日Dolby laboratory on DolbyAuthor: TigerMultichannel perceptual codingDolby AC-3is a kind of efficiency, quality and functional aspects with unprecedented effect perceptual digital audio coding technology. From the beginning of 1992, it has been for the cinema provide multichannel digital audio system and achieved in 1994into the two channel I BS application. It in the cassette and disc type family television system for transmitting multichannel digital sound function has been to the consumer electronics industry with very excited. In the United States, high definition television ( HDTV ) broadcasting the selected Dolby digital surround sound transmission, estimated that in 1996will be put into a test screening.Many have been announced and the potential applications of the technology of test shows, Dolby AC-3decoder has a beautifully versatility. AC-3 is not a single machine system, but a kind of use can make such as bit rate and number of channels such parameters to adapt to different special application flexible procedures for the treatment of familial. Various types of all decoder in order to work on the same principle as the foundation, and designed to take full account of the future need for compatibility and adaptability. Important is, Dolby AC-3will be high quality sound and excellent digital efficiency is very perfect combination. Because of the Dolby Laboratory for more than 20 years focus on human auditory research, in the development of signal processing field has accumulated rich experience, so, although AC-3than in the CD disk to the last channel lower bit rate to create a multi-channel surround sound, however, it makes the sound quality fully meet the listener expectations.Audio : past present and futureIn 30, the famous Baer Laboratories began using the three channel stereo sound. In 50, when the stereo into public movie, it uses the channel in four above, sometimes reaching over seven channels. A few years later, the stereo into families, since all of the phonograph records only with dual channel matching, so the family leave acoustic device only by dual channel playback, the technical limitations, can not the listener will generally two-channel stereo as the home audio selection criteria.But the film makers have channel 1( left, right, center ) and surround channel2as a compelling vivid sound minimum requirements. This can be from 70 time end, eighty time period the film industry widely adopted Dolby stereo to record film confirmed, Dolby stereo is the principle, let four channel matrix coding input two optical sound track, then an appropriate audio processor will restore it into four channels matrix coding reproduction.When Dolby stereo film is converted into audio signals, four channel coding retained the dubbing integrity, from 80 time begin first, Dolby surround has made multiple channel decoding into family time, today, tens of thousands of home audio systems are equipped with Dolby surround sound system, in fact, multi-channel surround sound system sales has been farbeyond the two-channel stereo system sales, at present, Dolby surround sound has been widely used in film, TV and music on CD recording studio, and its accompanying family Dolby surround systems on the market rapid development.With multi-channel audio in consumer electronics in the field of rapid growth, a more advanced technology was born, the technology is born there is nothing comparable to this, it has simulated realistic sound effects, and can satisfy various listening conditions and high demand cannot imagine adaptability, this is Dolby AC-3decoding technology Dolby AC-3 decoder, the successful development and application, is the world's electro-acoustic industry a major achievement.Dolby AC-3In 1987, high-definition television channel in the United States has officially become the standard process, its audio track is used for the first time in the four channel matrix encoding conversion for transmission of digital code stereo. However, by 1990, in order to avoid audio matrix are affected, four mono or stereo combined configuration as the optimal configuration. Due to time technical limitations, such an arrangement would have to increase by at least a bit rate.It is in this context, Dolby AC-3was born. It has the advantage of only two independent stereo more code rates can realize multi-channel audio code. Dolby advanced to the transmission of the code technology, such as Dolby AC-2 decoder for Dolby AC-3's successful development paved the way, but the complexity of multichannel code also need further research, including a new type of bit allocation technique.The Dolby laboratory is established by Rui Milton Dolby. Dr. Dolby was born in 1933 in the United States Portland Oregon City, grew up in the San Francisco Bay area. At the age of 16 he was still in high school, in Ampex company works. The company is the United States 's first production of magnetic tape recording equipment manufacturers. Later, he is responsible for the development of the company developed the world's first practical VCR portion of an electronic circuit.In 1957 Dolby graduated from Stanford University, University of Cambridge, Marshall won the British provided scholarships, study of L-band X light. In 1961 he received a doctor's degree in physics. In 1963, he accepted the UN appointed to India as a two-year consultant.As an amateur recording enthusiasts, Dr. Dolby over the years to recognize on the tape recording audio or video signal when background noise on the recording quality damage. While in India he began thinking seriously about a noise reduction without compromising the recording quality approach. His exploration of these became the Dolby A B noise reduction and noise reduction, noise reduction system based on C.In 1965, returning to England, in London he established his own laboratory in order to carry out in India he thought scheme. Set up in 1968 to" the Dolby lab" named company. Although the company was founded10 years ago, the work of the centre in the UK, but it has been an American company. After 1976, the company's main work moved to San francisco.In 1965, the first Dolby A type noise reducer ( A representing audio Audio ) production out of. The design of the system for a variety of audio noise reduction application, especially can solve the studio recording tape when the tape recorder generated noise. Until 1966, there have beenseveral noise reducing technology available, but they are much to damage the recording quality. So Dr Dolby faced difficulty is how to make the personage inside course of study and potential customers to believe his technique. At that time, multitrack recorder, from the 4 rail, track 8, track 16to 24 track, start the application, when multitrack recording tape audio mixing, the mixing of the two track tape noise level than double direct recording of the master tape is much higher.In 1966January, Decca Records UK Department believes that Dolby A type noise reducer can indeed as Dr. Dolby described that play a role, and then ordered9Dolby A301A type noise reducer, applied for the first time in 1966May in Vienna to record Ashe Ken that Qi played some of Mozart's piano concerto. In 1966November, Decca published the first application of Dolby A type noise reducer record by Georg Solti / Muller second symphony. Subsequently, the recording industry began to recognize and use a large amount of Dolby A type noise reduction system. Initially used only recorded classical music, when multitrack recording technology promotion, will be more widely applied. Soon, the whole world of professional and non-professional begin to" Dolby" with high quality recording together.With the hope that Dolby will be present and noise reduction technology for civilian recorder voice rising, in an American commercial tape recorder manufacturer KLH company 's urging,1967April Dolby lab started to develop more practical civil noise reduction technology, initially known as the" simplified Dolby system", which later became known as Dolby B type noise reduction technology. In the Dolby B noise reduction technology development is nearing completion, Dr. Dolby made the decision, Dolby laboratory will not civilian production of audio products, consumer electronics products, but to the manufacturers authorized Dolby technology has been very mature, then by manufacturers for production. By the end of 1974, the Dolby laboratory authorized manufacturers already amounted to 47, including all consumer audio equipment manufacturers.Thereafter, Dolby laboratory has developed a series of Technology: C type noise reduction, SR ( spectral recording ), S type noise reduction, HXPro, stereo surround Dolby, Dolby, Dolby Pro Logic, AC1, AC2, Dolby digital ( AC3), Dolby E. These techniques are widely used in civil and professional audio equipment, sound recording film, cinema playback apparatus, digital broadcast etc..In addition to the headquarters in San Francisco, Dolby laboratory at present in the world have established branches or liaison offices: Losangeles, Wootton Barcelona ( UK), London, Brisbane, New York, Tokyo, Shanghai, Beijing, Hongkong.AC-3 multi-channel frameDolby surround ( Dolby Surround ) is the original Dolby multichannel film analog format consumer version. In the production of Dolby surround sound, a 4Channel -- left, right, and surround sound channel audio information through matrix coding in two tracks on a record. The two tracks from stereo format program source such as a video and television broadcast program and carrying into the family, and decoded the original 4channels of information can be reduced and surround sound. Hundreds of thousands of home videos and TV shows by Dolby surround coding." Dolby surround ( Dolby Surround ) as the most primary surround sound standard, provides a 4channel surround sound support.Dolby surround and DTS surround is similar in that they are lossy digital compression technology. This is referred to as" emotional" data compression technique is based on the human psychoacoustics that possess sound characteristics -- for high level sensitive voices, while shielding the other is not sensitive to the sound development of.Because Dolby stereo is a coding technology of digital stereo, and decoding technique uses a direction identifying circuit or a directional logic circuit, so that the use of Dolby company this circuit technology of sound is called Dolby Pro Logic sound; with Dolby 's proprietary specific decoding technology is called a Dolby Pro logic decoder decoder.Of course, only with the use of Dolby to the logic function of the AV amplifier, played by Dolby sound recording software, can hear the true high fidelity digital stereo sound effect. Dolby digital systems will generally be5.1 channel sound compression to 384bps, and some CD with 448bps, the maximum to the 640bps; DTS usually use much larger bit rate --1536bps. If other conditions are the same, is a bit more quality is better, this assertion is wrong? Unfortunately, the answer to this question is not so easy, because the Dolby Digital ( abbreviated as DD ) and DTS data compression circuit is different. For example, a coding efficiency very low signal, even if the bit rate is very high, also just wasted bits and disc space, but does not improve sound quality. Once a system is said to be" transparent", increase the bit rate without causing it to improve the sound quality. In addition because the DTS bit rate higher than Dolby, need takes up more space, if the DVD disk capacity constraints, may produce adverse effects on image quality, or to increase the additional cd.Dolby Pro-Logic surround sound ( Dolby Pro Logic ) is Dolby developed a surround sound system. It is the four track stereo recording by a specific encoding means for the synthesis of two channel, the original left channel ( L ), the right channel ( R ), the center channel ( C ), surround channel ( S ) of the 4signal, encoded into LT, RT composite double channel signal, replay through the decoder will encoded two-channel composite signals LT and RT reduction for encoding the left, right, in around four, each stem and independent signal, amplified respectively input left, right, center and surround sound speakers.In order to playback symmetry reasons, surround speakers using the left and right surround speakers, respectively, from the output of the amplifier, so the business to Dolby Pro-Logic surround sound output called channel five. But due to a left, right surround sound speakers connected in a channel, the output is the same as the surround channel information, the essence is still four channel. The business also has six channels and seven channels Dolby Pro Logic AV amplifier. The six track is the central channel two amplifying circuit is respectively connected with the output, in left center speaker and right center speaker. But left, right center speaker connected to a center channel, it is essentially a four channel. Seven channel surround sound channels is divided into four channel output, i.e. left rear surround, right rear surround sound, and adopts four surround sound, which became a seven channel output. But the output of the seven track four surround speakers are connected in a surround channel, also can calculate the output of four sound channels. So with Dolby Pro logic decoder AV amplifier whether five channel output, six channels of output or the seven output channels, is essentially a four channel. Dolby Pro-Logic surround sound in the left, right, three channel frequency range can reach 20-20000Hz, can meet the full range of requirements, but surround channel frequency range is narrow, only 100-7000Hz.Dolby E is designed for digital TV broadcast and post-production and the design of aprofessional audio coding system. Using the Dolby E, a AES / EBU channel can send up to 8channels of high quality digital audio stream, and also can be loaded Dolby digital control data signals (often called the metadata, including the Dolby digital mono mode, dynamic range, type, output level automatic adjustment of parameters, to ensure that users can correct Dolby digital program ). Dolby E with its advanced coding algorithm and higher data transmission rate, can ensure the digital TV audio signals through as many as 10cycle coding - decoding or other editing process, and does not cause quality deterioration. Dolby E audio can be associated with various formats of video signal is a good match, won't because video interference blind audio, sound burr or other distortion. Dolby E audio and video frames in the sequence are completely corresponding, can achieve precise audio and video integrated editing. More importantly, by use of this new type of coding technology, the existing radio and television system without large-scale transformation can spread multi-channel digital TV audio signals, thereby greatly reducing the system cost.Dolby E application is in digital television stations intermediate transfer, from a local television program transmitted by satellite to another local TV station. Dolby E in conveying to the transmitting terminal will be converted to PCM audio, and then encoded into Dolby digital signal, transmitted to thousands of households. Therefore, consumers in the home can be directly received by Dolby E signal, but only receives a digital signal on channel 5.1Dolby. In order to avoid the confusion, usually Dolby E called transfer coding system, and Dolby will be called to launch digital coding system.Dolby E standard data transfer rate is 1.92Mbits / sec (20bit / 48kHz for audio signal ), typical operating mode is "5.1+2", using six channel transmits a 5.1channel surround sound signal, the other two channel transmission of two-channel matrix coding signal ( such as Dolby Pro-Logic surround sound ) or dual mono stereo signal. Can also work in other modes, such as with two mono signal"5.1+1+1" pattern, three way stereo signal "3x 2" mode and a six single channel signal"6x 1" mode. Dolby's current version supports 29.97fps frame rate ( NTSC standard, PAL25FPS ),20bit length and 48kHz sampling frequency of the audio signal, a future version will support25FPS,16bit or24bit audio signal.AC-3 transmission formAC-3 based transmission system into a more extensive application field is feasible in technology. At the end of the century before, several AC-3 based application technology into commercial production.High definition television ( HDTV ) is declared using a AC-3 code first application technology. Grand Alliance has selected the United States developed this technique. For its high definition television system with digital surround sound and in 1996Atlanta Olympic Games for the first time as media.Because the AC-3effects and can be associated with high definition television matches the standard features of digital cable TV system, therefore, is a natural candidate for AC - 3. The first test transmission was 1994year. Due to the current available programs can use a single sound, stereo can also use with matrix ( matrix - sur-round ) stereo, therefore, a AC-3dual channel decoder for has been developed. And when the multi-channel digital program for transmission, high function converter ( converter ) will create a synthetic stereo downwardmixing effect.Always as home theater the highest quality image source DVD ( (LD ) as Dolby surround digital multi-channel audio examples show. Using AC-3bit stream ( bit stream ) alternative FM channel in a channel, so that the stereo pulse code modulation ( PCM ) digital audio soundtrack with FM mono cooperate with each other, so that it can be compatible with existing any player. With cable, DBS and DAB is realized by AC-3spectrum effect, quality and multi channel features a unique mix of choice. The first use of AC-3DBS system has been introduced in 1994, it can be for commercial organizations to provide a single transmitter transmission up to 120 stereo music channel transmission system.Other areas of application include medical telemetry devices suitable for very low bit-rate code under development. Potential users and system developers and the Dolby laboratory, in order to obtain the AC-3 technical support.AC-3 integrated circuitDolby surround digital main technical progress is Rolland ( Irap ) Company IR38000, which is a can perform AC-3decoder to decode single chip digital sound field processor ( DSP ). It was first used in second generation Dolby stereo digital cinema in the decoding unit.A Rolland company development, lower cost, especially suitable for consumer electronics equipment and also can provide the program logic decoding ( Pro Logic decoding ) AC--3 decoder integrated circuit in the middle of 1994launch. This is a dual channel integrated circuit chip can be used, such as cable television 's top decoder. Other semiconductor manufacturers have been or are ready to supply the AC-3 decoder integrated circuit.Dolby and digitalAC-3 is Dolby's laboratory developed the third generation of perceptual coding system. Each code system will be a special psychological acoustics ( psycho acoustics ) knowledge and advanced digital signal processing technology combine very well.AC-1 initially by the Australian Broadcasting Corporation in 1985 for its DBS system. Perhaps partly because AC-1 decoder cost reasons, it appears to be widely applied to other DBS services, satellite communication network and digital" wired broadcasting system". According to their different applications, each channel code rate for 220-325bit / sec. As an adaptation of delta modulation ( ADM ) in the form of a digital stream, ( datastream) contains information not by audio signal absolute value provided, but by different sampling ( Sample ) value changes identified. By Dolby transform to noise reduction techniques, such as: continuous transformation step and pre-emphasis can greatly improve the adaptation of delta modulation ( ADM ) basic performance.Dolby AC-2advanced adaptive transmission code used in professional audio transmission and storage, which each channel digital rate of 128 or192day / sec. Narrow band multiplicity of frequency control signal program fully adopted the noise masking superiority, resulting in an efficient reduction rate and high signal transparent effect. In other applications, such as: a long distance transmission, real time (real-time ) recording, mixing and adding storage ( ADR ) are very widely used for connecting remote recording studio or film shooting field. AC =3 is alsoused to connect the BBC Transmitter Room and the Dolby DSTLR system core equipment. AC-3 is in the AC-1and AC-2is developed on the basis of multi channel coding technology, to retain the original AC - 2such as window function, exponential transform coding, adaptive bit allocation and many other features, but also a new stereophonic sound channel coding technology strategy for the coupling and rematrix algorithm. In general, the stereo left channel and a right channel signal in the sense of hearing is very similar, there are many repetitive redundancy information, will be the two channel signals combine to be coded, can remove redundant signal and will not affect the original sound quality. Here AC-3array low bit rate and an effective means of.AC-3PC voice data input, output the compressed digital bit stream. Coding is the first step, using the TDAC ( Time Domain Aliasing Cancellation ) filter the time-domain PC sampling data is transformed into a frequency domain blocks into a series of transform coefficients, each transform coefficient in binary exponential notation, namely an exponent and a mantissa. Exponent part encoded constitutes the entire signal substantially the spectrum, also known as the spectral envelope. Using the spectrum including and shaded by line correlation decision each mantissa bit allocation. Because the bit allocation is adopted in the anterior / posterior to the hybrid adaptive bit allocation and public bit pool technology, which can make the limited rate in the channel between the different frequency components, between the rational allocation of the mantissa; in quantization process, the mantissa is shaking, shaking the pseudo random number generator can be on a different platform to get the same results. By the end of six blocks of the spectral envelope, coarse quantization of the mantissa and the corresponding parameters consisting of AC-3 data frame format, continuous frame merged into a digital stream output.By the time domain is transformed to the frequency domain block length selection is the exponential transform coding based on. As defined in AC-3two length switching, a512sample value point of the long block, a256sample value point of short block. In the analysis of signal spectrum, to deal with the channel signal blocks cut made longer, so that you can get a better frequency resolution, but also can get higher coding efficiency. But long data block may contain a number of different possible recognition of noise, such as pre-echo. That is to say the ear due to time and frequency exists on the shadowing effect in the exponential transform coding is a contradiction, not at the same time, must plan as a whole processing. For the steady state signal, whose frequency varies with time transform slow, in order to improve the coding efficiency, requirement filter has good frequency resolution, which requires a long block; as for the rapidly changing signal, requires good time resolution, which requires a short block. In the encoder, the input signal after3Hz high-pass filter removes the DC component, and then through a8kHz high-pass filter out high-frequency components, with its energy are compared with a preset threshold, in order to detect the signal transient situation.AC-3based on the modified discrete cosine transform ( MDCT ) adaptive transform coding ( ATC ) algorithm. Although defined in AC-3 standard MDCT transform, but the actual using a N / 4IFFT ( FFT ), plus two simple Pre-IFFT and Post-IFFT as adjustment, in order to achieve a N IMDCT transform. ATC algorithm is an important consideration is based on auditory masking effect critical band theory, namely in the critical band within a voice to another voice signal shielding effect the most obvious. Therefore, dividing the band filter group to have fast enough to ensure that critical band frequency response, and noise attenuation is large enough,the time and frequency of noise within the defined in the masking threshold.The AC-3 encoder bit allocation technique, has been applied widely on the forward and backward adaptive bit allocation rule. Forward adaptive bit allocation method is the encoder calculation, and the bit allocation information explicitly incorporated into the stream of data bits, and is characterized in that the front end of the encoding process uses auditory model, thus modifying the model the receiving side decoding process has no effect; the disadvantage of reducing coding efficiency, because of the need to transfer the bit allocation information while occupying a part effective bits. To the adaptive method did not get encoder clear bit allocation information, but from a digital stream in which the bit allocation information, has the advantages of no occupation of the effective bits, thus has higher transmission efficiency. Its drawback is from received data to calculate the bit allocation, if the calculation is too complex to the rising cost of decoder. In addition, the decoder algorithm also with encoder auditory model change. AC-3using hybrid backward / forward adaptive bit allocation, in enhancing the rate and reduce the cost of strikes a balance between.AC-3 decoder decoding principle basically is encoded by the reverse process, firstly, the decoder must with the encoded data stream synchronization, and then from a data error correction of digital flow separation control data, system configuration, the encoded spectral envelope and the quantized mantissas and other content, according to the sound spectrum envelope to generate the bit allocation information, the mantissa part of inverse quantization, restoring the transform coefficient exponent and mantissa, after synthesis filter banks, the data from the frequency domain to time domain, the final output of the PCM sample signal reconstruction.Through the understanding of AC-3, you can see the AC-3technology makes full use of the human ear sensory model, according to the different properties of signal, to take the corresponding effective algorithm, achieved at a high quality under the premise of achieving a higher rate for the intended purpose, is a very efficient and economical digital audio compression system. AC-3 is the American digital television system of mandatory standard, is the European digital television system recommended standard, at the same time, AC-3or DVD system of compulsory standards. At present our country is the development and promotion of digital TV system, all have reasons to believe that AC-3 technology will have a good prospect of application.Dolby Chun chamber ( About DolbyLaboratoies ) from the analog noise reduction ( analog noisereduction ) to the digital code ( digitalcode ), Dolby has concentrated on rooted in laboratory to ear sound perception based audio processing development. In the process of development, Dolby has always been the emphasis is on the critical listening and tested. Either analog or digital program program, their results are the same, with low cost, greatly improves the efficiency of communication media. In some cases, it also for the improvement of new products, such as: Dolby surround sound ( DolbySurround ) and home theater ( home theater T ) make contribution.The Dolby laboratory consists of the following components: investment and Technology Development Engineering Department, occupation audio product design and manufacturing sector, experts the organization and distribution of all over the world in the field of support group. Dolby products from companies located in modern American and British manufacturing plant. Lyrics by the world's major consumer electronics manufacturers group; for each license。
外文原文：1 The TC35i mold piece introductionCurrently, domestic already beginning usage of the GSM mold piece have a lot, and these of function, method of using difference not big.What this design adoption is a Siemens TC35 the TC35i of the series.On this kind of wireless mold piece function and TC35 and permit, design tightly packed, consumedly contracted the physical volume of customer's product.The TC35i and GSM2/2 andpermit,dual-band(GSM900/GSM1800), RS232 the data connect, should mold piece and radio frequency electric circuit and Ji take and integral whole, provide toward the customer standard of AT order connect, is data, speech, short news and fax provide fast, credibility, safety of deliver, convenience customer of application development and design.2 Usely AT introductionThe follow is uselly the At.3 The PDU code ruleSend out short news in common use Text and PDU(Protocol Data Unit, agreement data unit) mode currently.The usage Text mode receive and dispatch a message code simple, realization get up very easy, but the biggest weakness be to can't receive and dispatch Chinese message;But PDU mode not only support Chinese message, also the ability send out English message.The PDU mode receive and dispatch a message can the usage be 3 kinds of to code:7-bit, 8-bit and UCS2 code.7-the bit code to used for send out common of ASCII character list, 8-bit code Be usually used for sending out data news, UCS2 code used for sending out Unicode character list.General PDU's code is constitute by ABCDEFGHIJKLM 13.A:The address length of the message center, 216 enter to make number(one word stanza)B:The number type of the message center, 216 enter to make number.C:Message center number, B+C length will from the data decision in the A.D:Document head word stanza, 216 enter to make number.E:Information type, 216 enter to make number.F:Drive call number length, 216 enter to make number.G:Drive call number type, 216 enter to make number, take value together B.H:Drive call number, length from data within F decision.I:Agreement marking, 216 enter to make number.J:The data code a project, 216 enter to make number.K:Term of validity, 216 enter to make number.L:Customer data length, 216 enter to make number.M:Customer's data, its length from the data decision in the L.Enactment in J adoption UCS2 code, here is the Unicode character list of Chinese-English.4 RS-232 InterfaceRS-232 is one of the normally used interfaces at any time, it not only built in every PC-set, but also built in any types of computers which are from microcontroller to host computers, and equipment connected with them. The general usage of RS-232 is to connect a modern, the other arrangements with RS-232 interfaces include printer, data collection module, testing device and control loop. RS-232 can be also used in the simple link of any type of computer.RS-232 is designed to deal with the communication between two arrangements with distance limitation from 50 to 100ft, which depend on Potter rate and type of electric cable. Because of wide application of RS-232 port, its other usage is to link another type of adapter converted form the port.For example, a simple loop changes a RS-232 into a RS-485 port. The port can be link with several devices by means of a long lead. Non-equilibrium lead is used to linked to RS-232. Although non-equilibrium should something avoidable, it only refers to the electric property of the signal in lead. In a non-equilibrium lead, signal voltage is applied to another lead, all has another technical term “signal end”. Advantages in RS-232RS-232 is used everywhere. Every PC-set has one or more RS-232 ports. The renewed computers sustain other serial interfaces like USB. But RS-232 can do many things which USB can’t do.In the micro-controller interface chip can be easily used to change into RS-232.The jointing distance can reach 50-100ft. Many external interfaces are not used for too long distance. The longest distance joint of USB can reach 16ft. The distance between parallel printer interface on the PC-set and the host computer can reach 10 to 15ft, or 30ft by using Type TEEE-1284B driver. But RS-232 can use the longer electric cable.If every RS-232 port is linked with a modern, Telephone network can used to send data in the rage of the world.For a double link, 3 leads are needed. A parallel circuit generally needs 8 data lines, two or more control signal lines and ground wires。
