| A | B |
|---|
| CDs are | 120mm in diameter, 1.2mm thick, and can store up to 800 MB of information |
| CDs are comprised of a layer of polycarbonate plastic, a layer of | reflective metal, and a coat of lacquer |
| A CD-ROM drive is comprised of the drive motor, | laser assembly, tracking mechanism, and the communication circuits. |
| The CD-ROM's tracking mechanism is a | motor and drive system that moves the lens into the correct position to access a specific area of the CD-ROM |
| The CD-ROM's communication circuits are used to | send the information read from the CD-ROM to the computer using the configured bus. |
| CD-ROM drives are categorized by | their case type, bus type, and read speed |
| Internal CD-ROM drives draw their power from the | power supply and are usually connected to the computer bus through a ribbon cable |
| External CD-ROM drives connect either directly to an external port on the | computer (such as USB, FireWire, or parallel) or to a controller installed in one of the computer's expansion slots (usually SCSI). |
| A bus is the communications pipeline between | a computer and the peripherals that are installed. |
| Common internal computer connections include | IDE and SCSI. |
| Most motherboards have built-in IDE | controllers and will automatically recognize that a CD-ROM drive has been installed. |
| IDE communication cables are | 40-pin ribbon cables that connect to the drive and the motherboard |
| some motherboards offer built-in SCSI solutions, most applications require that a | SCSI adapter be purchased and installed separately. |
| A CD-ROM drive read speed determines the rate at which | information can be pulled from the CD-ROM and sent to the communications bus. |
| In general, the higher the read speed rating on a CD-ROM drive, the | faster the drive. |
| The read speed of a CD-ROM drive is measured in multiples of | 150kb and denoted by a numeral followed by an "x". |
| A drive rated at 10x has a read speed of | 1500kb per second (or 10 times 150kb). |
| A drive rated at 100x may only be able to achieve that rate near the | center of the CD-ROM while only achieving a 40x rate at the outer tracks. |
| An internal CD-ROM drive uses the standard Molex power connector that supplies | 12 volts to other devices inside a PC. |
| the CD-ROM drive must be set to its proper operating status: | master, slave, and single drive. |
| A CD-ROM drive should be set as a master drive only if it is the | fastest drive on that particular IDE cable. |
| Most CD-ROM drives have a digital-audio cable that connects directly to | the sound card. |
| A CD-ROM containing a Digital-to-Analog Converter (DAC) will allow music to be | played through the computer's speakers without requiring any overhead processing. |
| CD recorders allow users to | "burn" their own CDs containing music, data, video, or any combination thereof. |
| CD-R | Compact Disc - Recordable |
| opaque | non-reflective |
| CD-R media cannot be | re-written to |
| A CD-R drive listed as 24x/40x has a write speed of | 24x and a read speed of 40x. |
| CD-R media adds a layer of translucent dye between the aluminum and plastic layers that allows light to | shine through to the aluminum layer then reflects the light back. |
| This reflective/non-reflective surface of a CD-R easily translates into | bits of data. |
| When a CD-R drive writes information to the CD-R media, a laser is used to | burn areas of the translucent dye to create opaque, non-reflective spots. |
| CD-RW | Compact Disc - Rewritable |
| unlike CD-R media, the CD-RW disc is mostly incompatible with | other CD reading drives. |
| CD-RW media is unique in that it includes a | phase-change compound layer between the aluminum and plastic layers. |
| CD-RW's phase-change compound is a special mix of | chemical elements that can change physical states at certain temperatures and remain in that state indefinitely. |
| When the CD-RW write laser is used to burn information to the disc, certain areas of the phase-change compound are | melted by super-heating and held in that phase by rapid cooling. |
| What makes a CD-RW drive unique is that they include a third eraser laser used to | slowly reheat melted areas of the phase-change compound into the crystalline state. |
| D-RW drives are rated by the | speed at which they write, rewrite, and read information. |
| As a PC technician, when copying any type of CD, it is highly recommended to be on the lookout for | copyright or licensing limitations |
