Modems Words and word combinations:

Widely used – широко используемый

modulate – превращение цифровых сигналов в аналоговые

demodulate – превращение цифровых сигналов опять в цифровые

to convert digital computer signals – превращает цифровые компьютерные сигналы

acoustic – звуковой

direct-connect – прямое соединение

less interference – менее подвержен помехам

the bound rate – норма предела, ограничений

Internal – внутренний

external – внешний

placed inside – размещенный внутри

own power supply – собственное энергоснабжение

outside the computer – за пределами компьютера

is connected to the computer via a cable – соединяется с компьютером через кабель

compatible equipment – совместимое оборудование

include speed of data transmission – включая скорость передачи данных

parity scheme – аналогичная, соответствующая схема

direction of traffic – направление движения

so forth – и так далее

printing of incoming text – печатать поступающий текст

storage of incoming data on disk – сохранять поступающие данные на диск

Modems are probably the most widely used data communications hardware in business. They are certainly the most familiar to microcomputer users who communicate with one another or with a larger computer. As you know the word modem is actually a contraction of modulate and demodulate; a modem’s basic purpose is to convert digital computer signals to analog signals for transmission over phone lines, then to receive these signals and convert them back to digital signals. Most modems are categorized according to how they connected to the telephone line: acoustic or direct-connect. For many years, the acoustic coupler was the most widely used. This type of modem holds the telephone receiver in two rubber cups. The connection is then made acoustically (by sound). However, they are very susceptible to noise, or interference. As a result, they are now considerednearly obsolete.

In contrast, the direct-connect modem allows the user to directly connect the computer to the telephone line. The direct connection results in less interference and allows the modem to easily transmit and receive data at speeds from 300m to 2,400 bits per second (bps, also called the baud rate). Some modems run at 9,600 to 19,600 bps, but these modems, used with mini-and mainframe computers, are often more expensive than many microcomputers.

Direct-connect modems are either internal or external. An internal modem is located on a circuit board that placed inside a microcomputer (actually plugged into an expansion slot). The internal modem draws its power directly from the computer’s power supply. No special cable is required to connect the modem to the computer.

An external direct-connected modem is an independent hardware component - that is, it is outside the computer- and users its own power supply.

The modem is connected to the computer via a cable designed for the purpose. A simple external modem designed to be used with a microcomputer costs less than $ 500; very fast, more complex modems can cost over several thousand dollars.

Business users who deal with modems and data communications must be sure they are communicating with compatible equipment; like other types of computer hardware and software, not all modems work with other modems, and not all modems work with the same type of software. In addition, microcomputer communications software packages systems at specific ’parameters’ so that their microcomputer can ‘talk’ to another computer using the same parameters. [Parameters include speed of data transmission, parity scheme, direction of traffic, and so forth. The software package manual tells users how to set software parameters and how to use a small screwdriver to set certain switches, called DIP (dual inline package) switches, in the external modem cabinet.] these software packages allow ‘smart’ modems (with certain types of chips) to do more than simply transmit and receive; for example, you can arrange for automatic dialing and transmission, printing of incoming text, and storage of incoming data on disk.