Modify Your CD-ROM to Watch DVD Movies

There are two types of CD-ROM drives we can mod:

24x to 40x,

40x or higher

Drives slower than 24x are too old to be modded.

24x to 40x CD ROMs

Laser Head Adjustments:

The track pitch of Cd's is 1.6 microns, and the track pitch of DVDs is only 0.8 microns. The minimum length of track pits of Cd's is 0.843mm, and the minimum length of track pits of DVDs is 0.293mm. That's why DVD discs can store much more data in the size of a CD.

      Pinpointing this situation, we need to adjust the laser head so it can read discs with smaller track pitch and shorter track pits. Open up the CD-ROM drive, do you see a lens on the rail? That's the laser head. On the side of the laser head, there's a screw you can adjust.

  This is the key of this mod.

This screw can adjust the size of the laser beam that lands on the disc.

     Referring to the above, after adjusting, the laser beam should be less than 0.293mm, to suit the needs of DVD discs. So turn that screw 2-3 times. I got this number through trial and error. Mark with a pencil, in case you forget how many times you turned that screw.

Speed adjustments:

DVD-ROM drives can play DVD movies smoothly at 4x speed. If we're modding a 32x CD-ROM drive, the rotation speed is obviously too high, increasing heat,and shortening the life of the drive.So we need to decrease the speed of it.

Most people know that power supplies can provide 5V (red wire) and 12V (yellow wire) electricity output for Molex connectors. Find the Molex connector you'll plug into the modded CD-ROM drive, cut the yellow wire or insulate it with tape, so only 5V of electricity is transferred to the CD-ROM drive.

The speed of the drive is now 32 * 5/17 = 9.41x and can now fulfill our requirements.

40x or higher CD ROMs

When 40x CD-ROM drives are released, most manufacturers are already producing DVD-ROM drives. To lower cost, they use the same core as DVD-ROM drives with DVD functions disabled. What we need to do here is to re-enable the DVD function.

Open up the CD-ROM, behind the circuit board, look for a jumper that says DVD JUMP. Find a jumper to connect this jumper. Thin metal wire also works fine. OK, so the DVD function is unlocked, but we still need to decrease the speed. Use the instructions above on how to decrease the speed of the drive.

WIRELESS LAN

INTRODUCTION:

    Wireless LAN (WLAN) is a flexible data communication system implemented as an extension to a wired LAN within a building or campus. WLANs transmit and receive data over the air by electrical signals, minimizing the need for wired connections. The advent of WLAN opened up a whole new definition of what a network infrastructure can be. No longer does an infrastructure need to be solid and fixed, difficult to move and expensive to change. Instead it can move with the user and change as fast as the organization does.

     Thus WLANs combine data connectivity with user mobility. Today it provides wireless access to vital network resources such as large, multi location enterprises, small and medium enterprises as well as hotels and hospitals, airports and homes. They are being widely recognized as viable, cost effective general purpose solution in providing real-time access to information and are reshaping the local area network landscape. 

    Wireless LANs are based on a set of technologies known by the IEEE specification number, 802.11 or by its synonymous trademarked name, Wi-Fi™ and is gaining popularity due to fact that it operates in the unlicensed ISM(Industrial Scientific & Medical) band (2.40 GHz to 2.484 GHz, 5.725 GHz to 5.850 GHz).

CHOICE OF WIRELESS TECHNOLOGY:

     The widespread reliance on networking in business and the meteoric growth of the Internet and online services are strong testimonials to the benefits of shared data and shared resources. With wireless LANs, users can access shared information without looking for a place to plug-in. Wireless LAN offers the following productivity and convenience over Wired Networks:

► Mobility

► Installation Speed and Simplicity

► Installation Flexibility

► Reduced Cost of Ownership

        ► Scalability

THE TECHNOLOGY:

    Wireless LANs are based on a set of technologies known by the IEEE specification number, 802.11 which was finalized in June 1997.The figure indicates the model developed by the 802.11 working group.

  Wireless LANs use electromagnetic airwaves (radio or infrared) to communicate information from one point to another without relying on any physical connection. Radio waves are responsible for delivering energy to a remote receiver. The data being transmitted is superimposed on the radio carrier so that they can be easily extracted at the receiving end. Once data is superimposed (modulated) onto the radio carrier, the radio signal occupies more than a single frequency, since the frequency or bit rate of the modulating information adds to the carrier.

  Multiple radio carriers can exist in the same space at the same time without inferring with each other if the radio waves are transmitted on different radio frequencies. To extract data a radio receiver tunes in one radio frequency while rejecting all other frequencies.

     The smallest building block of a wireless LAN is a Basic Service Set (BSS), which consists of some number of stations executing the same MAC protocol and competing for the access to the same shared medium. A BSS may be isolated or it may connect to a backbone distribution system through an Access Point (AP) which in a typical LAN configuration, is a transmitter/receiver (transceiver) device. The Access Point functions as a bridge. It receives buffers and transmits data between the wireless LAN and the wired network infrastructure. A single Access Point can support a small group of users and can function within a range of less than one hundred to several hundred feet. The Access Point (or the antenna attached to the AP) is usually mounted high but may be mounted essentially anywhere as long as radio coverage is obtained. End user access the Wireless LAN through Wireless-LAN adapters, which are implemented as PC cards.

   An Extended Service Set (ESS) consists of two or more basic service sets interconnected by a distribution system. The ESS appears as a single logical LAN to the Logical Link Control (LLC) level.

The standard defines three types of stations based on mobility:

► No Transition                     

► BSS Transition

► ESS Transition