Н. В. Моина ю. Б. Генина т. В. Шульженко чтение английской научнотехнической литературы
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How Do Touch-Screen Monitors Work?Touch-screen monitors have become more and more commonplace as their price has steadily dropped over the past decade. There are three basic systems that are used to recognize a person's touch: resistive, capacitive, and surface acoustic wave. The resistive system consists of a normal glass panel that is covered with a conductive and a resistive metallic layer. These two layers are held apart by spacers, and a scratch-resistant layer is placed on top of the whole setup. An electrical current runs through the two layers while the monitor is operational. When a user touches the screen, the two layers make contact in that exact spot. The change in the electrical field is noted and the coordinates of the point of contact are calculated by the computer. Once the coordinates are known, a special driver translates the touch into something that the operating system can understand, much as a computer mouse driver translates a mouse's movements into a click or a drag. In the capacitive system, a layer that stores electrical charge is placed on the glass panel of the monitor. When a user touches the monitor with his or her finger, some of the charge is transferred to the user, so the charge on the capacitive layer decreases. This decrease is measured in circuits located at each corner of the monitor. The computer calculates, from the relative differences in charge at each corner, exactly where the touch event took place and then relays that information to the touch-screen driver software. One advantage that the capacitive system has over the resistive system is that it transmits almost 90 % of the light from the monitor, whereas the resistive system only transmits about 75 %. This gives the capacitive system a much clearer picture than the resistive system. On the monitor of a surface acoustic wave system, two transducers (one receiving and one sending) are placed along the x and y axes of the monitor's glass plate. Also placed on the glass are reflectors: they reflect an electrical signal sent from one transducer to the other. The receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly. The wave setup has no metallic layers on the screen, allowing for 100% light throughput and perfect image clarity. This makes the surface acoustic wave system best for displaying detailed graphics (both other systems have significant degradation in clarity). Another area in which the systems differ is in which stimuli will register as a touch event. A resistive system registers a touch as long as the two layers make contact, which means that it doesn't matter if you touch it with your finger or a rubber ball. A capacitive system, on the other hand, must have a conductive input, usually your finger, in order to register a touch. The surface acoustic wave system works much like the resistive system, allowing a touch with almost any object (except hard and small objects like a pen tip). As far as price, the resistive system is the cheapest; its clarity is the lowest of the three, and its layers can be damaged by sharp objects. The surface acoustic wave setup is usually the most expensive. Internet-Based CommunicationsIf you use the Internet, then you probably use Internet-based communications to contact family, friends or co-workers. From sending an instant message to a friend, to e-mailing co-workers, to placing phone calls, to conducting video conferences, the Internet offers a number of ways to communicate. The advantages of Internet-based communications are many. Since you're already paying for an Internet account (or your employer is), you can save money on phone calls by sending someone an instant message or by using VoIP instead of standard local telephone services. Of course, no technology is without a downside and Internet-based communications has plenty, such as viruses, privacy issues and spam. Instant Messaging. One of the fastest-growing forms of Internet communications is instant messaging, or IM. Think of IM as a text-based computer conference between two or more people. An IM communications service enables you to create a kind of private chat room with another individual in order to communicate in real-time over the Internet. Typically, the IM system alerts you whenever somebody on your buddy or contact list is online. You can then initiate a chat session with that particular individual. One reason that IM has become so popular is its real-time nature. Unlike e-mail, where you will wait for the recipient to check his or her e-mail and send a reply, if a person you want to reach is online and available in your IM contact list, your message appears instantly in a window on their screen. While IM is used by millions of Internet users to contact family and friends, it's also growing in popularity in the business world. Employees of a company can have instant access to managers and co-workers in different offices and can eliminate the need to place phone calls when information is required immediately. Overall, IM can save time for employees and help decrease the amount of money a business spends on communications. While different IM clients offer slightly different features and benefits, the look and feel of an IM client is basically the same. Public IM clients and services available include ICQ, AOL Instant Messenger (AIM), Microsoft MSN Messenger, and Yahoo! Messenger. For businesses and enterprises looking for a more secure method of IM, there are enterprise IM packages available such as Microsoft Live Communication Server 2005 and IBM Lotus Instant Messaging. Third-party software is available to help businesses make using public IM services in the workplace more secure. Some problems and issues associated with IM include spim and virus propagation. Spim is the IM equivalent of spam and is perpetuated by bots that harvest IM screen names off of the Internet and simulate a human user by sending spim to the screen names via an instant message. The spim typically contains a link to a Web site that the spimmer is trying to market. Spim is a bit more intrusive than spam due to the nature of IM itself. These advertisements and junk messages will pop-up in your IM window and you need to deal with the messages immediately, where with e-mail you can usually filter a lot of it out and deal with it later. Additionally, viruses and Trojans can be spread through IM channels. These malicious programs are usually spread when an IM user receives a message that links to a Web site where the malicious code is downloaded. The message will appear to be from a known IM contact, which is why recipients are more likely to click the hyperlink and download the file. Using safe chat rules (such as never clicking the link) and keeping an updated anti-virus program on your system will help reduce the chances of becoming infected by malicious programs being spread through instant messaging. Internet Telephony & VoIP. Internet telephony consists of a combination of hardware and software that enables you to use the Internet as the transmission medium for telephone calls. For users who have free, or fixed-price Internet access, Internet telephony software essentially provides free telephone calls anywhere in the world. In its simplest form, PC-to-PC Internet telephony can be as easy as hooking up a microphone to your computer and sending your voice through a cablemodem to a person who has Internet telephony software that is compatible with yours. This basic form of Internet telephony is not without its problems, however. Connecting this way is slower than using a traditional telephone, and the quality of the voice transmissions is also not near the quality you would get when placing a regular phone call. Many Internet telephony applications are available. Some, such as CoolTalk and NetMeeting, come bundled with popular Web browsers. Others are stand-alone products. Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI) or Voice over IP (VoIP) products. VoIP is another Internet-based communications method which is growing in popularity. VoIP hardware and software work together to use the Internet to transmit telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions, called PSTN (Public Switched Telephone Network). The voice traffic is converted into data packets then routed over the Internet, or any IP network, just as normal data packets would be transmitted. When the data packets reach their destination, they are converted back to voice data again for the recipient. Your telephone is connected to a VoIP phone adapter (considered the hardware aspect). This adapter is connected to your broadband Internet connection. The call is routed through the Internet to a regular phone jack, which is connected to the receiver's phone. Special hardware (the phone adapter) is required only for the sender. Much like finding an Internet service provider (ISP) for your Internet connection, you will need to use a VoIP provider. Some service providers may offer plans that include free calls to other subscribers on their network and charge flat rates for other VoIP calls based on a fixed number of calling minutes. You most likely will pay additional fees when you call long distance using VoIP. While this sounds a lot like regular telephone service, it is less expensive than traditional voice communications, starting with the fact that you will no longer need to pay for extras on your monthly phone bill. E-mail. Short for "electronic mail", e-mail is the transmission of messages over communications networks. The messages can be notes entered from the keyboard or electronic files stored on disk. Most mainframes, minicomputers and computer networks have an e-mail system. Some e-mail systems are confined to a single computer system or network, but others have gateways to other computer systems, enabling you to send electronic mail anywhere in the world. Using an e-mail client (software such as Microsoft Outlook or Eudora), you can compose an e-mail message and send it to another person anywhere, as long as you know the recipient e-mail address. All online services and Internet Service Providers (ISPs) offer e-mail, and support gateways so that you can exchange e-mail with users of other systems. Usually, it takes only a few seconds for an e-mail to arrive at its destination. This is a particularly effective way to communicate with a group because you can broadcast a message or document to everyone in the group at once. One of the biggest black clouds hanging over e-mail is spam. Though definitions vary, spam can be considered any electronic junk mail (generally e-mail advertising for some product) that is sent out to thousands, if not millions, of people. Often spam perpetrates the spread of e-mail Trojans and viruses. For this reason, it's important to use an updated anti-virus program, which will scan your incoming and outgoing e-mail for viruses. IRC. Short for "Internet Relay Chat", IRC is a multi-user chat system that allows to people gather on "channels" or "rooms" to talk in groups or privately. IRC is based on a client/server model. That is, to join an IRC discussion, you need an IRC client (such a mIRC) and Internet access. The IRC client is a program that runs on your computer and sends and receives messages to and from an IRC server. The IRC server, in turn, is responsible for making sure that all messages are broadcast to everyone participating in a discussion. There can be many discussions going on at once and each one is assigned a unique channel. Once you have joined an IRC chat room (chat room discussions are designated by topics), you can type your messages in the public chat room where all participants will see it, or you can send a private message to a single participant. With many IRC clients you can easily create your own chat room and invite others to join your channel. You can also password protect your chat room to allow for a more private discussion with people whom you invite. Once you become familiar with your IRC client you'll find many options available to help you moderate and take part in a channel. One problem commonly associated with IRC is lag. IRC relies on the connections between the servers, and the connections or the servers can slow down. If you're in a discussion and people do not respond, or you notice that people are responding to things you types several minutes ago, then you can attribute this to lag. If you continue to experience lag, you can try connecting to the IRC network on a different server. Videoconferencing. Videoconferencing is a conference between two or more participants at different sites by using computer networks to transmit audio and video data. Each participant has a video camera, microphone and speakers connected on his or her computer. As the two participants speak to one another, their voices are carried over the network and delivered to the other's speakers, and whatever images appear in front of the video camera appear in a window on the other participant's monitor. In order for videoconferencing to work, the conference participants must use the same client or compatible software. Many freeware and shareware video-conferencing tools are available online for download, and most Web cameras also come bundled with videoconferencing software. Many newer video-conferencing packages can also be integrated with public IM clients for multipoint conferencing and collaboration. In recent years, videoconferencing has become a popular form of distance communication in classrooms, allowing for a cost efficient way to provide distance learning, guest speakers, and multi-school collaboration projects. Many feel that videoconferencing provides a visual connection and interaction that cannot be achieved with standard IM or e-mail communications. SMS & Wireless Communications. Short message service (SMS) is a global wireless service that enables the transmission of alphanumeric messages between mobile subscribers and external systems such as e-mail, paging and voice-mail systems. Messages can be no longer than 160 alpha-numeric characters and must contain no images or graphics. Once a message is sent, it is received by a Short Message Service Center (SMSC), which must then get it to the appropriate mobile device or system. As wireless services evolved, Multimedia Messaging Service (MMS) was introduced and provided a way to send messages comprising a combination of text, sounds, images and video to MMS capable handsets. Communication on wireless devices such as mobile phones and PDAs is frequently changing. Today you can use your wireless device to not only make phone calls, but to send and receive e-mail and IM. While you can use e-mail, IRC or IM for free if you have an Internet account, you will end up paying fees to you mobile carrier to use these services on a wireless device. |