11th Class Computer Science Chapter 3 Data Communication Short Questions Answers

In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. The half –duplex mode is like a one-lane road with traffic allowed in both directions.

Computer produce and consume data is groups of bits much as we conceive of and use spoken language in the form of words rather than letters. By grouping, we can send data n bits at a time instead of 1. This is called parallel transmission.

A fiber optics cable is a thin strand of glass that transmits beams of light rather than electric frequencies. When one end of the thread is exposed to light, the thread carries the light all the way to the other end, bending around corners with only a minute loss of energy along the way.

A communication satellite is a space station that receives microwave signals from earth microwave station. The earth based stations often are microwave stations.

Coaxial cable sometimes called coax is widely used for cable TV and is used in some net-works.

Modem, as a shortened form of Modulator/ Demodulator, allows the computer to convert data is useful information. When it receives an analog data through a connection, it has to convert it in digital data to be usable by the computer. Likewise it reverses the action when it has to send data.

A device that is used for receiving messages is called receiver. It is also known as sink. The receiver can be a computer, telephone set, printer, or a fax machine etc.

The decoder is an electronic device. It receives data from transmission medium. It converts in coded signals into digital form.

Guided media is also known as bounded media, coaxial cable, twisted pair cables and fiber optic cables is the example of bounded media, or guided media.

Digital signals is a sequence of voltage represented in binary form. The digital signals are in the form of electrical pulses of ON and OFF. These signals are in discrete form. Digital signals are faster and efficient.

Asynchronous data transmission is so named because the timing of a signal is unimportant. Instead, information is received and translated by agreed upon patterns. As long as those patterns are followed, the receiving device can retrieve the information without regard to the rhythm in which it is sent.

In full-duplex mode, both citations can transmit and receive simultaneously. The full-duplex mode is like a two say street with traffic flowing in both directions at the same time.

Analog signal is a continuous electrical signal in the form of wave. The wave is known as carrier wave. Telephone line is most commonly used media for analog signals.

Unicode stands for universal code. It is a 16-bit code. It can represent 65536 characters or symbols. It is developed by following the ASCII coding scheme. The first 265 codes in Unicode are identical to the 256 codes used by ASCII system.

An External modem can be used to the same purpose and in the same conditions as internal computer modem. However external modem is a small box that uses other kind of interfaces to be connected to the computer.

A computer accepts and processes data in binary form. Therefore, all data, numeric or non-numeric, must be converted into binary form before storing inside the computer. The process of conversion data into binary form is called encoding of data.

IEEE defines modulation as “a processes where by certain characteristics of wave, often called the carrier, are varied or selected in accordance with a modulation function”.

In simplex mode data is transmitted only in the way direction but in half duplex mode data can be transmitted in both directions. Simplex mode is faster than half duplex mode.

In serial transmission one bit follows another, so we need only one communication channel rather than to transmit data between two communication devices.

The basics component or elements of data communication system are as follows:

1. Message
2. Sender
3. Receiver
4. Medium or Communication Channel
5. Encoder and Decoder

The encoder is an electronic device. It receives data from sender in the form of digital signals. It converts digital signals into a form that can be transmitted through transmission medium. The decoder is an electronic device. It receives data from transmission medium. It converts encoded signals into digital form.

Broadband is high-speed internet connection provided through cable, DSL, Fiber, Radio, Signals, or Satellite.

The process of transferring data from one location to another or form one computer to another is called data communication. In this process, data is transmitted from one location to another by using transmission media.

Signal is an electromagnetic or light wave that represents data. Signals are used to transfer data from one device to another through a communication medium.

Modem is a communication device, which is used to send and receive data from one computer to another computer using telephone line. The modem is used to convert digital signal into analog signal and vice versa.