CHAPTER 13

CD/DVD Drives and Specifications Chapter 13
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for young children or those who work in harsh environments to use the discs without smudging or
damaging them due to excess handling.
The tray loader itself is also subject to damage. The trays can easily break if bumped or if something is
dropped on them while they are extended. Also, any contamination you place on the tray or disc is
brought right into the drive when the tray is retracted. Tray-loaded drives should not be used in a
harsh environment, such as a commercial or an industrial application. Make sure both the tray and
the data surface of the disc are clean whenever you use a tray-loading drive.
The tray mechanism also does not hold the disc as securely as the caddy. If you don’t have the disc
placed in the tray properly when it retracts, the disc or tray can be damaged. Even a slight misalignment
can prevent the drive from reading the disc properly, forcing you to open the tray and reset the
disc.
Some tray drives can’t operate in a vertical (sideways) position because gravity prevents proper loading
and operation. Check to see whether the drive tray has retaining clips, which grab the hub of the
disc. If so, you can run the drive in either horizontal or vertical position.
Some drives equipped with retaining clips still aren’t capable of running reliably in the vertical position.
If this is a critical feature for you, be sure to test a unit before you install it in a system, or make
sure you can return it if it doesn’t work properly.
Apart from the convenience, the other advantage of the tray mechanism over the caddy system is in
cost, and that is a big factor. If you do not have young children and plan to use the drive in a clean
environment where careful handling and cleanliness can be assured, the tray mechanism is recommended
because of its significantly lower cost.
Caddy
At one time, the caddy system was used on most high-end CD-ROM drives as well as the early CD-R
and DVD-RAM drives. It has since declined in popularity because of the convenience of the tray. The
caddy system requires that you place the disc itself into a special caddy, which is a sealed container
with a metal shutter. The caddy has a hinged lid that you open to insert the disc, but after that the lid
remains shut. When you insert the caddy containing the disc into the drive, the drive opens a metal
shutter on the bottom of the caddy, allowing access to the disc by the laser.
The caddy is not the most convenient loading mechanism, although if all your discs are in their own
caddies, all you have to do is grab the caddy containing the disc you want and insert it into the drive.
This makes the drive operate similar to a 3 1/2-inch disk. You can handle the caddy without worrying
about touching or contaminating the disc or the drive, making this the most accurate and durable
mechanism as well. Young children can easily handle the caddies and don’t have to touch the compact
discs themselves.
Because the caddy is sealed, the discs are protected from damage caused by handling. The only time
you actually handle the disc is when you first put it into the caddy. The caddy loading system also
ensures that the disc is properly located when inside the drive. This allows for more accurate laserhead
positioning mechanisms, and caddy drives generally have faster access times, as well.
The drawbacks to the caddy system are the expense and the inconvenience. You only get one caddy
with the drive, so if you want to store your discs in their own caddies, you must buy many more.
Additional caddies can cost $4–$10 each, which can lead to a significant expense if you have a large
number of discs.
The best application for caddy drives is in severe environments such as machine shops, repair shops,
factories, or anywhere somebody with dirty hands or gloves on will have to change discs.