LEARNING OBJECTIVES 1. Describe the various methods currently used to place computer print on paper. 2. Discuss characteristics of dot-matrix characters.

LEARNING OBJECTIVESLEARNING OBJECTIVES

1. Describe the various methods currently used to place computer print on paper. 2. Discuss characteristics of dot-matrix characters. 3. Discuss the types of paper handling common to different printer technologies. 4. Install and configure a printer for DOS or Windows operation. 5. List special considerations that must be observed when installing or repairing serial printers. 6. Identify a given type of cable connection between the printer and the computer. 7. Discuss data flow-control methods as they apply to serial printers. 8. Identify the major components of a dot matrix printer. 9. Describe troubleshooting techniques associated with dot-matrix printers.10. Relate symptoms to associated components in a dot-matrix printer.11. Describe general alignment procedures for printhead mechanisms.12. Describe the operation of a typical ink jet-printer.13. Identify the major components of an ink-jet printer.14. Describe troubleshooting techniques associated with ink-jet printers.

15. Relate symptoms to associated components in an ink-jet printer.16. Describe the process for applying print to a page in a laser printer.17. Identify the major components of a laser printer.18. Describe troubleshooting techniques associated with laser printers.19. Relate symptoms to associated components in a laser printer.

Figure 10-1: Typical Character Printer

Impact printers place characters on the page by Impact printers place characters on the page by causing a hammer device to strike an inked causing a hammer device to strike an inked ribbon. The ribbon, in turn, strikes the printing ribbon. The ribbon, in turn, strikes the printing surface (paper). surface (paper).

Figure 10-2: Fully-formed and Dot-Matrix Type Characters

Older non-impact printers relied on special heat-Older non-impact printers relied on special heat-sensitive or chemically reactive paper to form sensitive or chemically reactive paper to form characters on the page. Newer methods of non-characters on the page. Newer methods of non-impact printing use ink droplets, squirted from a impact printing use ink droplets, squirted from a jet-nozzle device or a combination of jet-nozzle device or a combination of laser/xerographic print technologies, to place laser/xerographic print technologies, to place characters on a page.characters on a page.

Basically, two methods exist for creating characters Basically, two methods exist for creating characters on a page. One method produces a character that is on a page. One method produces a character that is fully shaped and fully filled-in. This type of fully shaped and fully filled-in. This type of character is called a fully-formed character. The character is called a fully-formed character. The other method involves placing dots on the page in other method involves placing dots on the page in strategic patterns to fool the eye into seeing a strategic patterns to fool the eye into seeing a character. This type of character is referred to as a character. This type of character is referred to as a dot-matrix character.dot-matrix character.

Figure 10-3: The Daisy Wheel

Figure 10-4: Dot-Matrix Characters

Figure 10-5: Dot-Matrix Printer Pinheads

The term font refers to variations in the size and The term font refers to variations in the size and style of characters. With true fully-formed style of characters. With true fully-formed characters, typically only one font is available characters, typically only one font is available unless you change the physical printing element. unless you change the physical printing element. However, all other printing methods typically However, all other printing methods typically offer a wide variety of font types and sizes.offer a wide variety of font types and sizes.

Three common classifications of character fonts Three common classifications of character fonts exist: bit-mapped (or raster-scanned) fonts, exist: bit-mapped (or raster-scanned) fonts, vector-based fonts, and TrueType outline fonts.vector-based fonts, and TrueType outline fonts.

Figure 10-6: True Type Enabling Window

Figure 10-7: Windows Character Map

Figure 10-8: Rotating Drum and Chain Printers

Two types of impact line printers exist:

Rotating drum printers

Chain (or band) printers

By the very nature of their operation, printers tend By the very nature of their operation, printers tend to be extremely mechanical peripherals. During the to be extremely mechanical peripherals. During the printing operation, the print mechanism must be printing operation, the print mechanism must be properly positioned over each character cell in properly positioned over each character cell in sequence. sequence.

Figure 10-9: Printhead Carriage

In addition to positioning the print mechanism In addition to positioning the print mechanism for printing, all printer types must feed paper for printing, all printer types must feed paper through the print area. The type of paper-through the print area. The type of paper-handling mechanism in a printer is somewhat handling mechanism in a printer is somewhat dependent upon two factors: it speed and the dependent upon two factors: it speed and the type of form intended to be used with the type of form intended to be used with the printer.printer.

Figure 10-10: A Pin-Feed Tractor Mechanism

Two common methods exist for moving paper through the printer:

Friction-feedFriction-feed. Uses friction to hold the paper against the printer’s platen. The paper advances through the printer as the platen turns.

Pin-feedPin-feed. Pulls the paper through the printer by a set of pins that fit into the holes along the edge of the form, as shown in Figure 10-10. The pins may be an integral part of the platen or may be mounted on a separate, motor-driven tractor.

Figure 10-11: Common Printer Components

As with most other peripherals, the heart of a As with most other peripherals, the heart of a character printer is its interface/controller character printer is its interface/controller circuitry. The interface circuitry accepts data circuitry. The interface circuitry accepts data and instructions from the computer’s bus and instructions from the computer’s bus systems and provides the necessary systems and provides the necessary interfacing (serial or parallel) between the interfacing (serial or parallel) between the computer, and the printer’s control circuitry.computer, and the printer’s control circuitry.

In some printers, the microcontroller, RAM chips In some printers, the microcontroller, RAM chips or modules, and ROM/EPROM devices may be or modules, and ROM/EPROM devices may be treated as FRU components.treated as FRU components.

Generally speaking, one of the least difficult I/O Generally speaking, one of the least difficult I/O devices to add to a microcomputer system is a devices to add to a microcomputer system is a parallel printer. This is largely due to the fact parallel printer. This is largely due to the fact that, from the beginning of the PC era, a that, from the beginning of the PC era, a parallel printer has been one of the most parallel printer has been one of the most standard pieces of equipment to add.standard pieces of equipment to add.

Serial printers are slightly more difficult to set Serial printers are slightly more difficult to set up because the communication definition must up because the communication definition must be configured between the computer and the be configured between the computer and the printer. The serial port must be configured for printer. The serial port must be configured for speed, parity type, character frame, and speed, parity type, character frame, and protocol.protocol.

Figure 10-12: Printer Installation Steps

As with mice, printers require device driver As with mice, printers require device driver programs to oversee their operation.programs to oversee their operation.

Figure 10-13: Printer Driver Position

Serial printer problems basically fall into three categories:

Cabling problems

Configuration problems

Printer problems

Figure 10-14: Serial Printer Connection Schemes

Two popular methods of implementing software Two popular methods of implementing software flow control are Xon/Xoff and ETX/ACK. In the flow control are Xon/Xoff and ETX/ACK. In the Xon/Xoff method, special ASCII control Xon/Xoff method, special ASCII control characters are exchanged between the printer characters are exchanged between the printer and the computer to turn the data flow on and and the computer to turn the data flow on and off. In an ETX/ACK protocol, ASCII characters off. In an ETX/ACK protocol, ASCII characters for End-of-Text (ETX) and ACKnowledge for End-of-Text (ETX) and ACKnowledge (ACK) are used to control the movement of data (ACK) are used to control the movement of data from the port to the printer.from the port to the printer.

Figure 10-15: Software Flow Control

Figure 10-16: Windows 3.11 Printer Installation

Window

The components of a typical dot-matrix printer The components of a typical dot-matrix printer are depicted in Figure 10-17. They consist of a are depicted in Figure 10-17. They consist of a power supply board, a main control board, a power supply board, a main control board, a printhead assembly, a ribbon cartridge, a printhead assembly, a ribbon cartridge, a paper feed motor (along with its mechanical paper feed motor (along with its mechanical drive gears), and a printhead positioning motor drive gears), and a printhead positioning motor and mechanisms.and mechanisms.

Figure 10-17: Parts of a Dot-Matrix Printer

The control board is typically divided into four functional sections:

The interface circuitry

The character generation circuitry

The printer controller circuitry

Its motor control circuitry

Figure 10-18: Logical Parts of the Control Board

The status of the printer’s operation is monitored by the control board through a number of sensors:

Paper Out

Printhead Position

Home Position (for the printhead carriage)

Operator panel information includes the following:

Online

Form feed

Line feed

Power/paper out

Figure 10-19: A Parallel Connection at the Printer

The printhead is a collection of print wires set in The printhead is a collection of print wires set in an electromagnetic head unit. The printhead an electromagnetic head unit. The printhead assembly is made up of a permanent magnet, a assembly is made up of a permanent magnet, a group of electromagnets, and a housing. In the group of electromagnets, and a housing. In the printhead, the permanent magnet keeps the printhead, the permanent magnet keeps the wires pulled in until electromagnets are wires pulled in until electromagnets are energized, causing them to move forward.energized, causing them to move forward.

Figure 10-20: A Typical Dot-Matrix Printhead Control

Figure 10-21: Dot-Matrix Printhead

Figure 10-22: Installing a Tractor Assembly

The classical first step in determining the cause of The classical first step in determining the cause of any printer problem is to determine which part of any printer problem is to determine which part of the printer-related system is at fault: the host the printer-related system is at fault: the host computer, the signal cable, or the printer.computer, the signal cable, or the printer.

The following are symptoms for dot-matrix printer problems:

No lights or noise from printer

Light or uneven print produced

Printhead moving but not printing

Dots missing from characters

Printhead printing, but does not move

Paper will not advance

Typical dot-matrix configuration information includes the following:

Printer mode

Perforation skip (for continuous forms)

Automatic line feed at the bottom of the page

Paper-handling type

ASCII character codes (7-bit or 8-bit)

Basic character sets

Other quantities that can be set up include the following:

Print font

Character pitch

Form length

Typical fonts included in dot-matrix printers are listed here:

Draft

Courier

Prestige

Bold prestige

Figure 10-23: Disassemble the Printer

Figure 10-24: The Printer Carriage

Paper is specified in terms of its Weight per 500 Paper is specified in terms of its Weight per 500 sheets at 22 inches by 17 inches (that is, 500 sheets at 22 inches by 17 inches (that is, 500 sheets of 22 inches by 17 inches, 21-pound bond sheets of 22 inches by 17 inches, 21-pound bond paper weighs 21 pounds). paper weighs 21 pounds).

If the printhead does not operate, components involved can include the following:

The printhead

The flexible signal cable between the control board and the printhead

The control board

Possibly the power supply board

Figure 10-25: Adjusting the Printhead Spacing

Figure 10-26: Printhead’s Timing Belt

Ink-jet printers produce characters by squirting Ink-jet printers produce characters by squirting a precisely controlled stream of ink drops onto a precisely controlled stream of ink drops onto the paper, as illustrated in Figure 10-27. The the paper, as illustrated in Figure 10-27. The drops must be controlled very precisely in terms drops must be controlled very precisely in terms of their aerodynamics, size, and shape, or the of their aerodynamics, size, and shape, or the drop placement on the page becomes inexact and drop placement on the page becomes inexact and the print quality falters.the print quality falters.

Figure 10-27: Ink-Jet Printers

The drops are formed by one of two methods:

Thermal shockThermal shock heats the ink in a capillary tube, just behind the nozzle. This increases the pressure of the ink in the tube and causes it to explode through the opening.

Vibrations Vibrations from a piezo-electric crystal force ink through a nozzle.

Figure 10-28: Drop-on-Demand Printing

Figure 10-29: Continuous-Stream Printing

The primary components of a typical ink-jet printer are listed here:

The printhead assembly

The power board

The control board

The printhead positioning motor and timing belt

The paper feed motor and gear train

The printer’s sensors

Figure 10-30: Ink-Jet Printer Components

Figure 10-31: Ink-Jet Paper Handling

As with the dot-matrix printer, the first step in As with the dot-matrix printer, the first step in determining the cause of an ink-jet printer determining the cause of an ink-jet printer problem is to determine which part of the problem is to determine which part of the printer system is at fault: the host computer, printer system is at fault: the host computer, the signal cable, or the printer. the signal cable, or the printer.

These are symptoms of ink-jet printer problems:

No lights or noise from printer

Light or uneven print produced

Printhead moving but not printing, or printing erratically

Lines on the page

Printhead printing, but does not move

Paper will not advance

Typical configuration information includes the following:

Page orientation (landscape or portrait)

Paper size

Collation

Print quality

You can also configure the basic appearance of You can also configure the basic appearance of color and grayscale images produced by the color and grayscale images produced by the ink-jet printer. A color ink-jet printer uses four ink-jet printer. A color ink-jet printer uses four ink colors to produce color images: cyan, ink colors to produce color images: cyan, magenta, yellow, and black (referred to as magenta, yellow, and black (referred to as CMYK color). To create other colors, the CMYK color). To create other colors, the printer prints a predetermined percentage of printer prints a predetermined percentage of the basic colors in proximity to each other. the basic colors in proximity to each other.

Figure 10-32: Printer Case

The single item in an ink-jet printer that requires The single item in an ink-jet printer that requires the most attention is the ink cartridge (or the most attention is the ink cartridge (or cartridges). As the ink cartridge empties, the cartridges). As the ink cartridge empties, the printing eventually becomes faint and uneven, printing eventually becomes faint and uneven, and the resolution of the print on the page and the resolution of the print on the page diminishes.diminishes.

Figure 10-33: Self-Contained, Snap-in Ink Cartridge

If the printer does not print during the self-tests, the components involved include the following:

The printheadprinthead

The flexible signal cablesignal cable (between the control board and the printhead)

The control boardcontrol board

Possibly the power supply boardpower supply board

Figure 10-34: Printhead Positioning Components

The laser printer modulates a highly focused The laser printer modulates a highly focused laser beam to produce CRT-like raster-scan laser beam to produce CRT-like raster-scan images on a rotating drum, as depicted in images on a rotating drum, as depicted in Figure 10-35.Figure 10-35.

Figure 10-35: A Typical Laser Printer

The six stages of operation in a laser printer include the following:

Cleaning

Conditioning

Writing

Developing

Transferring

Fusing

To accomplish these objectives, all laser printers possess the following logical blocks:

Power supply

Control board

Laser-writing unit

Drum unit

Fusing assembly

Paper feed motor and gear train

System’s sensors

Control panel board

Figure 10-36: Block Diagram of a Laser Printer

As the laser writes on the drum, that drum As the laser writes on the drum, that drum turns through the toner powder, which is turns through the toner powder, which is attracted to the charged image on the drum.attracted to the charged image on the drum.

Figure 10-37: The Developer Roller

Figure 10-38: Transfer Process

Figure 10-39: H-P Cartridge Configuration

Figure 10-40: Laser Printer Basic Components

A typical laser printer has sensors to determine A typical laser printer has sensors to determine what paper trays are installed, what size paper what paper trays are installed, what size paper is in them, and whether the tray is empty. is in them, and whether the tray is empty. Sensors also track the movement of the paper Sensors also track the movement of the paper through each stage of the printer. This means through each stage of the printer. This means that the controller knows where the page is at that the controller knows where the page is at all times and can sequence the activities of the all times and can sequence the activities of the solenoids and clutches properly.solenoids and clutches properly.

Figure 10-41: Sensor Summary

Many of the problems encountered in laser printers Many of the problems encountered in laser printers are similar to those found in other printer types. are similar to those found in other printer types. For example, notice that most of the symptoms For example, notice that most of the symptoms listed in the following section relate to the printer listed in the following section relate to the printer not printing, not printing correctly, and not moving not printing, not printing correctly, and not moving paper through the printer. paper through the printer.

Basically, paper jams occur in all three main sections of the printer:

The pickup areapickup area

The registration arearegistration area

The fusing areafusing area

Unlike other printer types, the laser printer tends Unlike other printer types, the laser printer tends to have several high-voltage and high-to have several high-voltage and high-temperature hazards inside it. To get the laser temperature hazards inside it. To get the laser printer into a position where you can observe its printer into a position where you can observe its operation, you must defeat some interlock operation, you must defeat some interlock sensors. This action places you in potential sensors. This action places you in potential contact with the high-voltage, high-temperature contact with the high-voltage, high-temperature areas mentioned above. Take great care when areas mentioned above. Take great care when working inside the laser printer.working inside the laser printer.

The following are symptoms of laser printer problems:

The printer is dead, power is on, but no printing occurs.

The print on the page is light or washed out.

A blank page is produced.

Stains or black dust appear on the paper.

Vertical lines appear on the paper.

The printer will not load paper.

The paper jams in the printer.

A paper jam has been cleared, and the unit still indicates a jam is present.

If the printer’s fans and lights are working, other components that are associated with a defective power supply include the following:

Main motor and gear train

High-voltage corona wires

Drum assembly

Fusing rollers

Four basic reasons can explain why the main motor may not run when the printer is supposed to print:

The portion of the power supply that supplies the motor is defective.

The control circuitry is not sending the enabling signals to turn on the motor.

The motor is dead.

The gear train is bound up and will not let the motor turn.

Normal print-delivery problems fall into eight categories:

Black pages

White (blank) pages

Faint print

Random specks on the page

Faulty print at regular intervals on the page

White lines along the page

Print missing from some portion of the page

Smudged print

Figure 10-42: Paper Tray Sensors

Figure 10-43: The Paper Path

Normally the system should be setup so that the following are true:

TTEnable=1

TTifCollisions=0

TTOnly=0

Figure 10-44: The Windows Printer Setup Window

KEY POINTS REVIEWKEY POINTS REVIEW

Impact printers place characters on the page by causing a hammer device to strike an inked ribbon. The ribbon, in turn, strikes the paper.


Older non-impact printers relied on special heat-sensitive or chemically reactive paper to form characters on the page. Newer methods use ink droplets, squirted from a jet-nozzle device, or a combination of laser/xerographic print technologies to place characters on a page.


Two basic methods exist for creating characters on a page. One method places a character that is fully shaped and fully filled-in on the page. This type of character is called a fully-formed character. The other method involves placing dots on the page in strategic patterns to fool the eye into seeing a character. This type of character is referred to as a dot-matrix character.


The term font refers to variations in the size and style of characters. With true fully-formed characters, typically only one font is available unless you change the physical printing element. Three common categories of character fonts exist: bit-mapped (or raster-scanned) fonts, vector-based fonts, and TrueType outline fonts.


By the very nature of their operation, printers tend to be extremely mechanical peripherals. During the printing operation, the print mechanism must be properly positioned over each character cell in sequence.


In addition to positioning the print mechanism for printing, all printer types must feed paper through the print area. The type of paper-handling mechanism in a printer is somewhat dependent upon two considerations: its speed and the type of form intended to be used with the printer.


As with most other peripherals, the heart of a character printer is the interface/controller that accepts data and instructions from the computer’s bus systems and provides the necessary interfacing between the computer and the printer’s control circuitry.


In some printers, the microcontroller, RAM chips or modules, and the ROM/EPROM devices may be treated as FRU components.


One of the least difficult I/O devices to add to a microcomputer system is a parallel printer. From the beginning of the PC era, the parallel printer has been one of the most standard pieces of equipment to add.


Serial printers are slightly more difficult to set up because the communication definition must be configured between the computer and the printer. The serial port must be configured for speed, parity type, character frame, and protocol.


As with mice, printers require device driver programs to oversee their operation.


Two popular methods of implementing software flow control are Xon/Xoff and ETX/ACK. In the Xon/Xoff method, special ASCII control characters are exchanged between the printer and the computer to turn the data flow on and off.


The components of a typical dot-matrix printer include a power supply board, a Main control board, a printhead assembly, a ribbon cartridge, a paper feed motor (along with its mechanical drive gears), and a printhead positioning motor and mechanisms.


The printhead is a collection of print wires set in an electromagnetic head unit. The printhead assembly is made up of a permanent magnet, a group of electromagnets, and a housing.


The first step in determining the cause of any printer problem is to isolate the part of the printer-related system at fault: the host computer, the signal cable, or the printer.


Paper is specified in terms of its weight per 500 sheets at 22 inches by 17 inches (that is, 500 sheets of 22-by-17-inch, 21-pound bond paper weighs 21 pounds).


Ink-jet printers produce characters by squirting a precisely controlled stream of ink drops onto the paper. The drops must be controlled very precisely in terms of their aerodynamics, size, and shape, or the drop placement on the page becomes inexact.


A color ink-jet printer uses four ink colors to produce color images: cyan, magenta, yellow, and black (referred to as CMYK color). To create other colors, the printer prints a predetermined percentage of the basic colors in proximity to each other.


The single item in an ink-jet printer that requires the most attention is the ink cartridge(s)


The laser printer modulates a highly focused laser beam to produce CRT-like raster-scan images on a rotating drum.


As the laser writes on the drum turns through the toner powder, which is attracted to the charged image on the drum.


A typical laser printer has sensors to determine what paper trays are installed, what size paper is in them, and whether the tray is empty. The printer also uses sensors to track the movement of the paper through each stage of the printer.


Many of the problems encountered in laser printers include the printer not printing, not printing correctly, and not moving paper.


The laser printer tends to have several high-voltage and high-temperature hazards inside it. You may have to defeat some interlock sensors. This action places you in potential contact with the printer’s high-voltage, high-temperature areas. Take great care when working inside the laser printer.

REVIEW QUESTIONSREVIEW QUESTIONS

11 Referring to the Hardware Checks sections of the troubleshooting procedures for all three printer types, describe three general types of problems common to all printers. Describe the additional type of problem that dot-matrix and ink-jet printers have.


22 What are the common transmission parameters that must be set up for a serial printer interface?


33 Describe the purpose for using pin-feed mechanisms to move paper through the printer.


44 Describe the reason for using tractor-feed paper handling.


55 If the resolution of an ink-jet printer becomes unacceptable, what action should be taken?


66 Describe the function of the fuser assembly in a laser printer.


77 Describe the function of the primary corona (conditioning roller) in a laser printer.


88 If a laser printer continues to show a paper jam problem after the paper has been cleared, what type of problem is indicated, and what action should be taken?


99 List the three primary areas where paper jams occur in a laser printer, as well as any other areas where jams are likely to occur.


1010 Describe two methods used by ink-jet printers to put ink on the page.


1111 Does a successful self-test indicate that the printer is not the cause of the problem? List the parts of the system that can still be problem causes if the self-test runs successfully.


1212 How does a dot-matrix printer actually deliver ink to a page?


1313 What functions do the printer’s controller typically perform?


1414 List four things that can be damaging to the photosensitive surface of the laser printer’s drum.

MULTIPLE CHOICE QUESTIONSMULTIPLE CHOICE QUESTIONS

11 List three common pin configurations for dot-matrix printers.

a. 10, 20, and 30 pins b. 5, 10, and 15 pins c. 9, 18, and 24 pins d. 3, 6, and 9 pins


22 Name the four basic components of a laser printer cartridge.

a. Laser, toner supply, drum, and fuser b. Toner supply, corona wire, drum assembly, and developing roller c. Laser, toner supply, corona wire, and drum d. Toner supply, corona wire, drum assembly, and fuser


33 What is the purpose of the primary corona wire in a laser printer?

a. It cleans the paper as it enters the printer. b. It conditions the drum for printing. c. It transfers toner from the drum to the paper. d. It fuses the toner to the paper.


44 What is the first action that should be taken, if the print generated by a dot-matrix printer becomes faded, or uneven?

a. Change the ribbon cartridge. b. Add ink. c. Adjust the print carriage. d. Add toner.


55 What is the first action that should be taken if the print generated by a laser printer becomes faded or uneven?

a. Adjust the contrast control. b. Change the ink cartridge. c. Check the toner cartridge. d. Adjust the print mechanism.


66 What type of electrical charge must be placed on the corona wire to transfer toner from the drum to the paper?

a. Negative b. None c. Neutral d. Positive


77 List the six stages of a typical laser printer.

a. Pick up, registration, transfer, printing, fusing, and finishing b. Pick up, conditioning, transfer, developing, fusing, and finishing c. Cleaning, conditioning, writing, developing, transferring, and fusing d. Cleaning, registration, writing, transferring, fusing, and finishing


88 List the fundamental parts of a dot-matrix printer.

a. Power supply, microprocessor, tractor feed motor, printhead mechanism, and printhead positioning motor b. Power supply, interface board, paper feed motor, printhead mechanism, printhead positioning motor, and sensors c. Interface board, ink cartridge, printhead mechanism, printhead positioning motor, and sensors d. Controller, paper feed motor, ribbon cartridge, and printhead positioning motor


99 What type of ink delivery system is normally found in ink-jet printers built for the personal computers?

a. Drop-on-demand ink delivery b. Continuous-stream ink delivery c. Impact ink delivery d. Compact-spray ink delivery


1010 Describe what the specification for 60-pound bond paper means.

a. 100 22-by-17-inch sheets weigh 60 pounds b. 500 8.5-by-17-inch sheets weigh 60 pounds c. 100 11-by-17-inch sheets weigh 60 pounds d. 500 22-by-17-inch sheets weigh 60 pounds

LEARNING OBJECTIVES 1. Describe the various methods currently used to place computer print on paper. 2. Discuss characteristics of dot-matrix characters.

Documents

dotmatrix characters

printer types

window slide

parallel printer

common printer components

dotmatrix printers

dotmatrix printer pinheads

laser printers