(Hardware)
Keyboard
one of the main input devices used by computers is a keyboard, which looks very similar to the keyboards of electric typewriters, with some additional keys. But the keyboard is an amazing piece of technology. For instance, did you know that the keyboard on a typical computer system is actually a computer itself?
At its essence, a keyboard is a series of switches connected to a microprocessor that monitors the state of each switch and initiates a specific response to a change in that state. In this edition, you will learn more about this switching action, and about the different types of keyboards, how they connect and talk to your computer, and what the components of a keyboard are.
Types of Keyboards
Keyboards have changed very little in layout since their introduction. In fact, the most common change has simply been the natural evolution of adding more keys that provide additional functionality.
The most common keyboards are:
a. 101-key Enhanced keyboard
b. 104-key Windows keyboard
c. 82-key Apple standard keyboard
d. 108-key Apple Extended keyboard
a. 101-key Enhanced keyboard
b. 104-key Windows keyboard
c. 82-key Apple standard keyboard
d. 108-key Apple Extended keyboard
AT keyboard (101-Keyboard)
Also known as the 101-key keyboard, the AT keyboard is the US
104 keyboards
Also known as the Windows keyboard, the 104-key keyboard is a keyboard found with most new computers today that incorporates three additional Microsoft Windows keys.
Portable computers such as laptops quite often have custom keyboards that have slightly different key arrangements than a standard keyboard. Also, many system manufacturers add specialty buttons to the standard layout. A typical keyboard has four basic types of keys:
a. Typing keys
b. Numeric keypad
c. Function keys
d. Control keys
The typing keys are the section of the keyboard that contains the letter keys, generally laid out in the same style that was common for typewriters. This layout, known as QWERTY for the first six letters in the layout, was originally designed to slow down fast typists by making the arrangement of the keys somewhat awkward! The reason that typewriter manufacturers did this was because the mechanical arms that imprinted each character on the paper could jam together if the keys were pressed too rapidly. Because it has been long established as a standard, and people have become accustomed to the QWERTY configuration, manufacturers developed keyboards for computers using the same layout, even though jamming is no longer an iss
The numeric keypad is a part of the natural evolution mentioned previously. As the use of computers in business environments increased, so did the need for speedy data entry. Since a large part of the data was numbers, a set of 17 keys was added to the keyboard. These keys are laid out in the same configuration used by most adding machines and calculators, to facilitate the transition to computer for clerks accustomed to these other machines.
In 1986, IBM extended the basic keyboard with the addition of function and control keys. The function keys, arranged in a line across the top of the keyboard, could be assigned specific commands by the current application or the operating system. Control keys provided cursor and screen control. Four keys arranged in an inverted T formation between the typing keys and numeric keypads allow the user to move the cursor on the display in small increments. The control keys allow the user to make large jumps in most applications. Common control keys include:
a. Home
b. End
c. Insert
d. Delete
e. Page Up
f. Page Down
g. Control (Ctrl)
h. Alternate (Alt)
j. Escape (Esc)
a. Typing keys
b. Numeric keypad
c. Function keys
d. Control keys
The typing keys are the section of the keyboard that contains the letter keys, generally laid out in the same style that was common for typewriters. This layout, known as QWERTY for the first six letters in the layout, was originally designed to slow down fast typists by making the arrangement of the keys somewhat awkward! The reason that typewriter manufacturers did this was because the mechanical arms that imprinted each character on the paper could jam together if the keys were pressed too rapidly. Because it has been long established as a standard, and people have become accustomed to the QWERTY configuration, manufacturers developed keyboards for computers using the same layout, even though jamming is no longer an iss
The numeric keypad is a part of the natural evolution mentioned previously. As the use of computers in business environments increased, so did the need for speedy data entry. Since a large part of the data was numbers, a set of 17 keys was added to the keyboard. These keys are laid out in the same configuration used by most adding machines and calculators, to facilitate the transition to computer for clerks accustomed to these other machines.
In 1986, IBM extended the basic keyboard with the addition of function and control keys. The function keys, arranged in a line across the top of the keyboard, could be assigned specific commands by the current application or the operating system. Control keys provided cursor and screen control. Four keys arranged in an inverted T formation between the typing keys and numeric keypads allow the user to move the cursor on the display in small increments. The control keys allow the user to make large jumps in most applications. Common control keys include:
a. Home
b. End
c. Insert
d. Delete
e. Page Up
f. Page Down
g. Control (Ctrl)
h. Alternate (Alt)
j. Escape (Esc)
(The Windows keyboard adds some extra control keys: two Windows or Start keys and an Application key)
Inside the Keyboard
The processor in a keyboard has to understand several things that are important to the utility of the keyboard, such as:
a. The microprocessor and controller circuitry of a keyboard.
b. Position of the key in the key matrix.
c. The amount of bounce and how to filter it.
d. The speed at which to transmit the typematics.
a. The microprocessor and controller circuitry of a keyboard.
b. Position of the key in the key matrix.
c. The amount of bounce and how to filter it.
d. The speed at which to transmit the typematics.
The key matrix is the grid of circuits underneath the keys. In all keyboards except for capacitive ones, each circuit is broken at the point below a specific key. Pressing the key bridges the gap in the circuit, allowing a tiny amount of current to flow through. The processor monitors the key matrix for signs of continuity at any point on the grid.
When it finds a circuit that is closed, it compares the location of that circuit on the key matrix to the character map in itsROM.
A different character map provided by the computer can supersede the character map in the keyboard. This is done quite often in languages whose characters do not have English equivalents. Also, there are utilities for changing the character map from the traditional QWERTY to another custom version
Keyboards rely on switches that cause a change in the current flowing through the circuits in the keyboard. When the key presses the key switch against the circuit, there is usually a small amount of vibration between the surfaces, known as bounce. The processor in a keyboard recognizes that you pressing the key repeatedly do not cause this very rapid switching on and off. Therefore, it filters all of the tiny fluctuations out of the signal and treats it as a single key press.
If you continue to hold down a key, the processor determines that you wish to send that character repeatedly to the computer. This is known as typematics. In this process, the delay between each instance of a character can normally be set in software, typically ranging from 30 characters per second (cps) to as few as two cps.
When it finds a circuit that is closed, it compares the location of that circuit on the key matrix to the character map in its
A different character map provided by the computer can supersede the character map in the keyboard. This is done quite often in languages whose characters do not have English equivalents. Also, there are utilities for changing the character map from the traditional QWERTY to another custom version
Keyboards rely on switches that cause a change in the current flowing through the circuits in the keyboard. When the key presses the key switch against the circuit, there is usually a small amount of vibration between the surfaces, known as bounce. The processor in a keyboard recognizes that you pressing the key repeatedly do not cause this very rapid switching on and off. Therefore, it filters all of the tiny fluctuations out of the signal and treats it as a single key press.
If you continue to hold down a key, the processor determines that you wish to send that character repeatedly to the computer. This is known as typematics. In this process, the delay between each instance of a character can normally be set in software, typically ranging from 30 characters per second (cps) to as few as two cps.
From the Keyboard to the Computer
As you type, the processor in the keyboard is analyzing the key matrix and determining what characters to send to the computer. It maintains these characters in a buffer of memory that is usually about 16 bytes large. It then sends the data in a stream to the computer via some type of connection. The most common keyboard connectors are:
a. 5-pin DIN (Deustche Industrie Norm) connector
b. 6-pin IBM PS/2 mini-DIN connector
c. 4-pin USB (Universal Serial Bus) connector
d. Internal connector (for laptops
Normal DIN connectors are rarely used anymore. Most computers use the mini-DIN PS/2 connector; but an increasing number of new systems are dropping the PS/2 connectors in favor of USB. No matter which type of connector is used, two principal elements are sent through the connecting cable. The first is power for the keyboard. Keyboards require a small amount of power, typically about 5 volts, in order to function. The cable also carries the data from the keyboard to the computer
The other end of the cable connects to a port that is monitored by the computer's keyboard controller. This is an integrated circuit (IC) whose job is to process all of the data that comes from the keyboard and forward it to the operating system. When the operating system is notified that there is data from the keyboard, a number of things can happen:
a. It checks to see if the keyboard data is a system level command. A good example of this is Ctrl-Alt-Delete on a Windows computer, which initiates a reboot.
b. The operating system then passes the keyboard data on to the current application.
c. The current application understands the keyboard data as an application-level command. An example of this would be Alt - f, which opens the File menu in a Windows application.
d. The current application is able to accept keyboard data as content for the application (anything from typing a document to entering a URL to performing a calculation), or
e. The current application does not accept keyboard data and therefore ignores the information.
Once the keyboard data is identified as either system-specific or application-specific, it is processed accordingly. The really amazing thing is how quickly all of this happens. As I type this article, there is no perceptible time lapse between my fingers pressing the keys and the characters appearing on my monitor. When you think about everything the computer is doing to make each single character appear, it is simply incredible.
Keyboard Key Explanations
When talking to technical support or to other people about keyboard commands, you may hear such things as forward slash, backward slash, and caret. Many times this can be confusing for users unfamiliar with each of the symbols found on a keyboard. Below is a chart that can be used to quickly identify keyboard keys. Please keep in mind that some of these symbols will not be on all keyboards. We have tried to list each of the symbols found in all keyboards around the world.
a. 5-pin DIN (Deustche Industrie Norm) connector
b. 6-pin IBM PS/2 mini-DIN connector
c. 4-pin USB (Universal Serial Bus) connector
d. Internal connector (for laptops
Normal DIN connectors are rarely used anymore. Most computers use the mini-DIN PS/2 connector; but an increasing number of new systems are dropping the PS/2 connectors in favor of USB. No matter which type of connector is used, two principal elements are sent through the connecting cable. The first is power for the keyboard. Keyboards require a small amount of power, typically about 5 volts, in order to function. The cable also carries the data from the keyboard to the computer
The other end of the cable connects to a port that is monitored by the computer's keyboard controller. This is an integrated circuit (IC) whose job is to process all of the data that comes from the keyboard and forward it to the operating system. When the operating system is notified that there is data from the keyboard, a number of things can happen:
a. It checks to see if the keyboard data is a system level command. A good example of this is Ctrl-Alt-Delete on a Windows computer, which initiates a reboot.
b. The operating system then passes the keyboard data on to the current application.
c. The current application understands the keyboard data as an application-level command. An example of this would be Alt - f, which opens the File menu in a Windows application.
d. The current application is able to accept keyboard data as content for the application (anything from typing a document to entering a URL to performing a calculation), or
e. The current application does not accept keyboard data and therefore ignores the information.
Once the keyboard data is identified as either system-specific or application-specific, it is processed accordingly. The really amazing thing is how quickly all of this happens. As I type this article, there is no perceptible time lapse between my fingers pressing the keys and the characters appearing on my monitor. When you think about everything the computer is doing to make each single character appear, it is simply incredible.
Keyboard Key Explanations
When talking to technical support or to other people about keyboard commands, you may hear such things as forward slash, backward slash, and caret. Many times this can be confusing for users unfamiliar with each of the symbols found on a keyboard. Below is a chart that can be used to quickly identify keyboard keys. Please keep in mind that some of these symbols will not be on all keyboards. We have tried to list each of the symbols found in all keyboards around the world.
~ | Tilde |
` | Acute, Back quote, grave, grave accent, left quote, open quote, or a push |
! | Exclamation mark, Exclamation point, or Bang |
@ | At or At symbol |
# | Octothorpe, Number, Pound, or Hash |
£ | Pounds Sterling or Pound |
€ | Euro |
$ | Dollar sign |
¢ | Cent sign |
¥ | Japanese Yen |
¤ | Generic currency |
µ | Micro |
% | Percent |
° | Degree |
^ | Caret or Circumflex |
& | Ampersand or And |
* | Asterisk |
( | Open parenthesis |
) | Close parenthesis |
- | Hyphen, Minus or Dash |
_ | Underscore |
+ | Plus |
= | Equals |
{ | Open Brace |
} | Close Brace |
[ | Open bracket |
] | Close bracket |
| | Pipe, Or, or Vertical bar |
\ | Backslash or Reverse Solidus |
/ | Forward slash, Solidus, Virgule, or Whack |
§ | Section |
: | |
; | Semicolon |
" | Quote, Quotation mark, or Inverted commas |
' | Apostrophe or Single Quote |
< | Less Than or Angle brackets |
> | Greater Than or Angle brackets |
, | Comma |
. | Period or Full Stop |
? | Question Mark |
Microsoft Windows Shortcut Keys
Shortcut Keys | Description |
Alt + Tab | Switch between open applications. |
Alt + Shift + Tab | Switch backwards between open applications. |
Alt + Print Screen | Create a screen shot only for the program you are currently in. |
Ctrl + Esc | Bring Up start button. |
Alt + Esc | Switch Between open applications on taskbar. |
F2 | Renames selected Icon |
F3 | Starts find from desktop |
F4 | Opens the drive selection when browsing. |
F5 | Refresh Contents |
Alt + F4 | Closes Current open program. |
Ctrl + F4 | Closes Window in Program |
Ctrl + (the '+' key on the keypad) | Automatically adjust the width's of all the columns in Windows explorer |
Alt + Enter | Opens properties window of Selected icon or program. |
Shift + F10 | Simulates right click on selected item. |
Shift + | Delete programs/files without throwing into the recycle bin. |
Holding Shift | Boot safe mode or by pass system files. |
Holding Shift | When putting in an audio CD will prevent CD Player from playing. |
Windows Keyboard Shortcuts
Below is a listing of Windows keys that can be used on computers running a Microsoft Windows operating system and using a keyboard with a Windows key. In the below list of shortcuts the windows key is represented by "WINKEY".
Shortcut Keys | Description |
WINKEY + D | Minimizes all windows and returns the user to the desktop. |
WINKEY + M | Minimizes all windows. |
WINKEY + SHIFT + M | To undo the minimize. |
WINKEY + E | Open Microsoft Explorer. |
WINKEY + Tab | Cycle through open programs through the taskbar. |
WINKEY + F | Display the Windows Search / Find feature. |
WINKEY + CTRL + F | Display the search for computers window. |
WINKEY + F1 | Display the Microsoft Windows help. |
WINKEY + R | Open the run window. |
WINKEY + Pause / Break key | Open the system properties window. |
WINKEY + U | Open Utility Manager. |
WINKEY + L | Lock the computer (Windows XP and above only). |
Mouse
It is an input device that rolls on a bearing and has buttons on the top. When rolled on across a flat surface, the mouse guides a cursor on a visual display screen in the direction of mouse’s movement. Mice first broke onto the public stage in 1984, and since then they have helped to redefine the way we use computers. Every day of your computing life, you reach out for your mouse whenever you want to move your cursor or activate something. Your mouse senses your motion and your clicks and sends them to the computer so it can respond appropriately.
Printer
A hardware device responsible for taking computer data and generating a hard copy of that data. It prints text or illustrations on paper. There are many different types of printers. In terms of the technology utilized, printers fall into the following categories:
a. Daisy-Wheel. Similar to a ball-head typewriter, this type of printer has a plastic or metal wheel on which the shape of each character stands out in relief. A hammer presses the wheel against a ribbon, which in turn makes an ink stain in the shape of the character on the paper. Daisy-wheel printers produce letter-quality print but cannot print graphics.
b. Dot-Matrix. It creates characters by striking pins against an ink ribbon. Each pin makes a dot, and combinations of dots form characters and illustrations.
c. Ink-jet. It sprays ink at a sheet of paper. Ink-jet printers produce high-quality text and graphics.
d. Laser. It uses the same technology as copy machines. Laser printers produce very high quality text and graphics.
e. LCD & LED. It is similar to a laser printer, but uses liquid crystals or light-emitting diodes rather than a laser to produce an image on the drum.
f. Line Printer. It contains a chain of characters or pins that print an entire line at one time. Line printers are very fast, but produce low-quality print.
g. Thermal Printer. An inexpensive printer that works by pushing heated pins against heat-sensitive paper. Thermal printers are widely used in calculators and fax machines.
Printers are also classified by the following characteristics:
a. Quality of type. The output produced by printers is said to be either letter quality (as good as a typewriter), near letter quality, or draft quality. Only daisy-wheel, ink-jet, and laser printers produce letter-quality type. Some dot-matrix printers claim letter-quality print, but if you look closely, you can see the difference.
b. Speed. It is measured in characters per second (cps) or pages per minute (ppm), the speed of printers varies widely. Daisy-wheel printers tend to be the slowest, printing about 30 cps. Line printers are fastest (up to 3,000 lines per minute). Dot-matrix printers can print up to 500 cps, and laser printers range from about 4 to 20 text pages per minute.
c. Impact or Non-Impact. Impact printers include all printers that work by striking an ink ribbon. Daisy-wheel, dot-matrix, and line printers are impact printers. Non-impact printers include laser printers and ink-jet printers. The important difference between impact and non-impact printers is that impact printers are much noisier.
d. Graphics. Some printers (daisy-wheel and line printers) can print only text. Other printers can print both text and graphics.
e. Fonts. Some printers, notably dot-matrix printers, are limited to one or a few fonts. In contrast, laser and ink-jet printers are capable of printing an almost unlimited variety of fonts. Daisy-wheel printers can also print different fonts, but you need to change the daisy wheel, making it difficult to mix fonts in the same document.
a. Daisy-Wheel. Similar to a ball-head typewriter, this type of printer has a plastic or metal wheel on which the shape of each character stands out in relief. A hammer presses the wheel against a ribbon, which in turn makes an ink stain in the shape of the character on the paper. Daisy-wheel printers produce letter-quality print but cannot print graphics.
b. Dot-Matrix. It creates characters by striking pins against an ink ribbon. Each pin makes a dot, and combinations of dots form characters and illustrations.
c. Ink-jet. It sprays ink at a sheet of paper. Ink-jet printers produce high-quality text and graphics.
d. Laser. It uses the same technology as copy machines. Laser printers produce very high quality text and graphics.
e. LCD & LED. It is similar to a laser printer, but uses liquid crystals or light-emitting diodes rather than a laser to produce an image on the drum.
f. Line Printer. It contains a chain of characters or pins that print an entire line at one time. Line printers are very fast, but produce low-quality print.
g. Thermal Printer. An inexpensive printer that works by pushing heated pins against heat-sensitive paper. Thermal printers are widely used in calculators and fax machines.
Printers are also classified by the following characteristics:
a. Quality of type. The output produced by printers is said to be either letter quality (as good as a typewriter), near letter quality, or draft quality. Only daisy-wheel, ink-jet, and laser printers produce letter-quality type. Some dot-matrix printers claim letter-quality print, but if you look closely, you can see the difference.
b. Speed. It is measured in characters per second (cps) or pages per minute (ppm), the speed of printers varies widely. Daisy-wheel printers tend to be the slowest, printing about 30 cps. Line printers are fastest (up to 3,000 lines per minute). Dot-matrix printers can print up to 500 cps, and laser printers range from about 4 to 20 text pages per minute.
c. Impact or Non-Impact. Impact printers include all printers that work by striking an ink ribbon. Daisy-wheel, dot-matrix, and line printers are impact printers. Non-impact printers include laser printers and ink-jet printers. The important difference between impact and non-impact printers is that impact printers are much noisier.
d. Graphics. Some printers (daisy-wheel and line printers) can print only text. Other printers can print both text and graphics.
e. Fonts. Some printers, notably dot-matrix printers, are limited to one or a few fonts. In contrast, laser and ink-jet printers are capable of printing an almost unlimited variety of fonts. Daisy-wheel printers can also print different fonts, but you need to change the daisy wheel, making it difficult to mix fonts in the same document.
Scanner
An input device that allows a user to take an image or text and convert it into a digital file allowing the computer to read or display the scanned object is known as Scanner. A scanner is commonly connected to a computer USB, Parallel or SCSI port. A scanner works by digitizing an image -- dividing it into a grid of boxes and representing each box with either a zero or a one, depending on whether the box is filled in. Scanners differ from one another in the following respects:
a. Scanning Technology. Most scanners use charge-coupled device (CCD) arrays, which consist of tightly packed rows of light receptors that can detect variations in light intensity and frequency. The quality of the CCD array is probably the single most important factor affecting the quality of the scanner. Industry-strength drum scanners use a different technology that relies on a photo multiplier tube (PMT), but this type of scanner is much more expensive than the more common CCD -based scanners.
b. Resolution. The denser the bit map, the higher the resolution. Typically, scanners support resolutions of from 72 to 600 dpi.
c. Bit Depth. The number of bits used to represent each pixel. The greater the bit depth, the more colors or grayscales can be represented. For example, a 24-bit color scanner can represent 2 to the 24th power (16.7 million) colors. Note, however, that a large color range is useless if the CCD arrays are capable of detecting only a small number of distinct colors.
d. Size and shape. Some scanners are small hand-held devices that you move across the paper. These hand-held scanners are often called half-page scanners because they can only scan 2 to 5 inches at a time. Hand-held scanners are adequate for small pictures and photos, but they are difficult to use if you need to scan an entire page of text or graphics.
a. Scanning Technology. Most scanners use charge-coupled device (CCD) arrays, which consist of tightly packed rows of light receptors that can detect variations in light intensity and frequency. The quality of the CCD array is probably the single most important factor affecting the quality of the scanner. Industry-strength drum scanners use a different technology that relies on a photo multiplier tube (PMT), but this type of scanner is much more expensive than the more common CCD -based scanners.
b. Resolution. The denser the bit map, the higher the resolution. Typically, scanners support resolutions of from 72 to 600 dpi.
c. Bit Depth. The number of bits used to represent each pixel. The greater the bit depth, the more colors or grayscales can be represented. For example, a 24-bit color scanner can represent 2 to the 24th power (16.7 million) colors. Note, however, that a large color range is useless if the CCD arrays are capable of detecting only a small number of distinct colors.
d. Size and shape. Some scanners are small hand-held devices that you move across the paper. These hand-held scanners are often called half-page scanners because they can only scan 2 to 5 inches at a time. Hand-held scanners are adequate for small pictures and photos, but they are difficult to use if you need to scan an entire page of text or graphics.
CD Writer
A device that allows you to create your own CD's for backup is called CD Writer. When you see a configuration on the front panel of CD Writer that looks like 12x2x24 (three numbers separated by the letter "x"), these numbers indicate the drive speeds of the drive. The "x" stands for the transfer of 150 KB of data per second, and each number represents a different action that the drive can take. A Writer has two actions -- recording onto and reading from compact discs. When looking at the drive speeds, the first number ("12" in the above example) indicates the speed at which the CD drive will record data onto disc. So, in the above example, the drive will record data at 12 times 150 KB/second. The second number ("2" in the above example) indicates the speed at which the CD Writer will rewrite data onto a CD-RW compact disc. So in the above example, the CD drive will rewrite data onto the compact disc at 2 times 150 KB/second. Typically, the second number, the rewrite speed, is lower than the first number, the write speed, because rewriting is a slower process than writing. The last number ("24" in the above example) indicates the speed at which the drive will read data from a compact disc. So in the above example, the CD Writer will read data from a compact disc at 24 times 150 KB/second.
Fax Machine
A device that can send or receive pictures and text over a telephone line is called Fax Machine. Fax machines work by digitizing an image -- dividing it into a grid of dots. Each dot is either on or off, depending on whether it is black or white. Electronically, each dot is represented by a bit that has a value of either 0 (off) or 1 (on). In this way, the fax machine translates a picture into a series of zeros and ones (called a bit map) that can be transmitted like normal computer data. On the receiving side, a fax machine reads the incoming data, translates the zeros and ones back into dots, and reprints the picture.
The idea of fax machines has been around since 1842, when Alexander Bain invented a machine capable of receiving signals from a telegraph wire and translating them into images on paper. In 1850, aLondon
But while the idea of fax machines has existed since the 1800s, fax machines did not become popular until the mid 1980s. The spark igniting the fax revolution was the adoption in 1983 of a standard protocol for sending faxes at rates of 9,600 bps. The standard was created by the CCITT (Abbreviation of Comité Consultatif International Téléphonique et Télégraphique, an organization that sets international communications standards) standards organization and is known as the Group 3 standard. Now, faxes are commonplace in offices of all sizes. They provide an inexpensive, fast, and reliable method for transmitting correspondence, contracts, résumés, handwritten notes, and illustrations.
A fax machine consists of an optical scanner for digitizing images on paper, a printer for printing incoming fax messages, and a telephone for making the connection. The optical scanner generally does not offer the same quality of resolution as stand-alone scanners. Some printers on fax machines are thermal, which means they require a special kind of paper. Some of the features that differentiate one fax machine from another include the following:
a. Speed. Fax machines transmit data at different rates, from 4,800 bps to 28,800 bps. A 9,600-bps fax machine typically requires 10 to 20 seconds to transmit one page.
b. Printer Type. Most fax machines use a thermal printer that requires special paper that tends to turn yellow or brown after a period. More expensive fax machines have printers that can print on regular bond paper.
c. Paper Size. The thermal paper used in most fax machines comes in two basic sizes: 8.5-inches wide and 10.1-inches wide. Some machines accept only the narrow-sized paper.
d. Paper cutter. Most fax machines include a paper cutter because the thermal paper that most fax machines use comes in rolls. The least expensive models and portable faxes, however, may not include a paper cutter.
e. Paper feed. Most fax machines have paper feeds so that you can send multiple-page documents without manually feeding each page into the machine.
The idea of fax machines has been around since 1842, when Alexander Bain invented a machine capable of receiving signals from a telegraph wire and translating them into images on paper. In 1850, a
But while the idea of fax machines has existed since the 1800s, fax machines did not become popular until the mid 1980s. The spark igniting the fax revolution was the adoption in 1983 of a standard protocol for sending faxes at rates of 9,600 bps. The standard was created by the CCITT (Abbreviation of Comité Consultatif International Téléphonique et Télégraphique, an organization that sets international communications standards) standards organization and is known as the Group 3 standard. Now, faxes are commonplace in offices of all sizes. They provide an inexpensive, fast, and reliable method for transmitting correspondence, contracts, résumés, handwritten notes, and illustrations.
A fax machine consists of an optical scanner for digitizing images on paper, a printer for printing incoming fax messages, and a telephone for making the connection. The optical scanner generally does not offer the same quality of resolution as stand-alone scanners. Some printers on fax machines are thermal, which means they require a special kind of paper. Some of the features that differentiate one fax machine from another include the following:
a. Speed. Fax machines transmit data at different rates, from 4,800 bps to 28,800 bps. A 9,600-bps fax machine typically requires 10 to 20 seconds to transmit one page.
b. Printer Type. Most fax machines use a thermal printer that requires special paper that tends to turn yellow or brown after a period. More expensive fax machines have printers that can print on regular bond paper.
c. Paper Size. The thermal paper used in most fax machines comes in two basic sizes: 8.5-inches wide and 10.1-inches wide. Some machines accept only the narrow-sized paper.
d. Paper cutter. Most fax machines include a paper cutter because the thermal paper that most fax machines use comes in rolls. The least expensive models and portable faxes, however, may not include a paper cutter.
e. Paper feed. Most fax machines have paper feeds so that you can send multiple-page documents without manually feeding each page into the machine.
f. Autodialing. Fax machines come with a variety of dialing features. Some enable you to program the fax to send a document at a future time so that you can take advantage of the lowest telephone rates.
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