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Picture Tube of TV Receiver The picture tube of a television receiver is a cathode ray tube (CRT) employing magnetic deflection. The picture sent out by the transmitting station is reproduced in the Picture tube. In the picture tube, the electron beam is deflected by a magnetic field. The magnetic deflection is obtained with the help of horizontal and vertical deflection coils in the yoke around the tube neck. The deflection provide the scanning of the beam on the fluorescent screen of the tube. The picture signal is fed to the grid of the electron gun. The instantaneous value of the pictures signal thus controls the instantaneous beam current and hence the brightness of the spot on the screen. In this way, the picture elements scanned at the television camera tube in the transmitter are reproduced on the fluorescent screen of the picture tube. When the screen is viewed from a distance, the tiny picture elements blend in a smooth way to produce the impression of a continuous p

what is Monitor? Out of all the output devices, monitor is perhaps the most important, because it is the output device that people interact with most intensively. Computer information is displayed, visually with a video adapter card and monitor. Information processed within the CPU, that needs to be visually displayed, is sent to video adapter. The video adapter converts information from the formal used, in the same manner as a television displays information sent to it by a cable service. TWO BASIC TYPES OF MONITORS ARE USED WITH MICROCOMPUTERS, WHICH ARE AS FOLLOWS: 1.       CRT 2.       LCD Cathode Ray Tube (CRT): The first is the typical monitor that you see on a desktop computer. It looks a lot like a television screen, and works the same way. This type uses a large vacuum tube, called cathode ray tube (CRT). Liquid Crystal Displays: The second type, known as a flat panel monitor, is commonly used with notebook computer. Most of these employ liq

what is Printer/ define         After a document is created on the computer, it can be sent to a printer for a hard copy (printout). Same printers offers special features such as coloured and large page formats. Some of the most commonly used printers are: 1.       Laser Printer 2.         Dot Printer 3.       Ink Jet Printer 4.       Line Printer Laser Printer: A laser printer produces high quality print that one normally finds in publishing. It is extremely fast and quiet. Moreover, the operation of a laser printer is extremely easy with automatic paper loading and no smudging or messing up of ink ribbons. Most laser printers output 6 to 12 pages per minute. Minimum buffer memory in a laser printer is 1 MB. Dot Matrix Printer: The dot matrix printer (DMP, in short) is a very versatile and inexpensive output device and is suitable for most of our computing jobs. In a DMP the print head physically “hits” the paper through the ribbon and produces text (or im

What is Modem and Fax Modem: A modem enables your computer your computer to receive/send data from/to remote places through telephone lines, to the other computer provided each has a compatible modem. These are attached to serial port of the computer. Modems are used to connect a computer to a remote network through dial-up or leased line connections. A modem is controlled by using a communication program. Some of the On-line services, one can avail through a modem, are: “Electronics mail” “Banking and travel reservations” “File transfers” “Fax Services” “Internet access” Modem of varying speeds, measurable in Megabits per second (Mbps), are available in the market. Some of the common speeds are 14.4 Mbps, 28.8 Mbps, 33.7 Mbps and 56.4 Mbps. Fax: In the present day computer system, FAX machines can be attached with A COMPUTER IS SEND AND RECEIVE DOCUMENTS CREATED IN THE COMPUTER TO DISTANT PLACES, BRINGING COMPUTERS AND COMMUNICATION toget

What is Input Devices? Input devices accept data and instructions from the user. Following are the examples of various input devices, which are connected to the computer to provide input. There are many input devices. Some important input devices are as follows: 1.       Keyboard 2.       Mouse 3.       Joystick 4.       Light Pen 5.       Optical/magnetic Scanner 6.       Touch Screen 7.       Microphone for voice as input 8.       Track Ball 1.       Keyboard: A keyboard is the most common input device now. Several kinds of keyboards are available, but they resemble each other with minor variations. The keyboard in most common use is the QWRTY board (from keys Q, W, E, R, T, Y in the top left corner of the keyboard). IBM and IBM compatible PCs or microcomputers use 104 keyboard; so called since it has 104 keys. In these keyboards, the cursor control keys are duplicated to allow easier use of the numeric pad. 2.       Mouse: A mouse is an electro-m

What is Satellite Communication? For sky wave propagation, usually the frequency band extending from 3 to 30 MHz is employed. Radio links over long distance over the earth surface can be established by multi-hop transmission. But reliable communication by means of sky waves is hampered due to problems like fading, ionospheric disturbance and storms. Artificial satellite offer reliable communication links over long distance. An artificial satellite is hurled into space in a circular orbit in the equatorial plane at height of 36000 km above the surface of the earth.  The period of revolution of the satellite round the earth is 24 hours, i.e., equal to the period of rotation of the earth about in own axis. So, to an observer on the earth’s surface, the satellite appears to be stationary. Such satellite are therefore referred to a geostationary satellite and the orbit as the synchronous orbit.  The wave containing information is transmitted to the satellite from a transmit

                                       What is Antenna? Antennas or aerials are necessary for the radiations or reception of radio wave which are electromagnetic in character. A system of elevated conductors that couple or match the transmitter or the receiver to space, can serves as antenna. A transmission line is employed to connect the transmitting antenna to the transmitter. In according with Maxwell’s theory, electromagnetic energy having the same frequency as the RF current flowing through the antenna, is radiated in space For a straight-wire antenna, the radiation COMPARISION AN ELECTRIC FIELD VECTOR IN A PLANE CONTAINING THE ANTENNA, AND A MAGNETIC FIELD VECTOR TRANSVERES TO THE ELECTRIC FIELD.  The electric and the magnetic fields oscillate At the frequency of the RF currents in the antenna. The amplitudes of the fields vary directly as the amplitude of the RF current, and they fall off inversely as the distance from the antenna. The fields travel through the spa

What is Secondary Storage (External Storage Device)? Floppy diskettes, hard disk, taps and optical disks come under the category of external storage device or ancillary storage device. These devices are very sensitive to environmental conditions (humidity and temperature) as well as to external magnetic fields and need to be stored carefully. Types of external storage device are as follows: 1.       Floppy disk 2.       Hard disk 3.       Tape 4.       Optical disk 1.       Floppy disk: It is magnetic storage media, using flat circular platter. Floppy disks are primarily used on PCs . Information on a floppy disk is recorded in the magnetized states of particles of iron oxides evenly placed upon concentric circles known as Tracks. Tracks are further divided into sectors. The difference between the capacities of double density and the quad density diskettes is in the number of tracks per inch (tpi)- 48 tpi and 996 tpi. Respectively, and in the number of sectors pe