ADSL Hardware in Software

Maker PDF417 in Software ADSL Hardware

In order for the ADSL subscriber to connect to the local CO, a splitter will be connected to the phone jack in the wall The splitter will then connect to the phone and also to the ADSL modem, as shown in Figure 8-12 This splitter is essentially a frequency lter The human voice falls between 0 and 34 KHz, so the splitter sends transmissions below 34 KHz to the telephone, and transmissions above 34 KHz are sent to the ADSL modem The ADSL modem has an RJ-45 jack that is used to connect to the network card in the PC It is not really a modem in the sense of a modem that converts digital signals to analog signs; this modem is really just acting as a terminal adapter Asymmetric Digital Subscriber Line (ADSL) uses different download and upload speeds (asymmetric), whereas Symmetric Digital Subscriber Line (SDSL) uses an equivalent upload and download bandwidth; home users typically use ADSL, but businesses most often use SDSL

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Figure 8-13 displays an actual ADSL modem and splitter The splitter, if needed, would connect to the phone jack in the wall, and then the computer would connect to the ADSL modem A number of ADSL modems have the lter built into the modem so the lter wall plate may not be needed

If the phone companies are going to offer high-speed Internet service through the phone lines, you can bet that the cable companies would come up with a broadband, high-speed Internet solution using the coaxial cable TV lines The cable companies connect you to the Internet over their lines by using a cable modem that connects to the workstation using TP cabling, but then the modem connects to the cable jack in the wall using coaxial cable (as shown in Figure 8-14) The cable provider supplies each channel on the cable in its own 6-MHz frequency range, and the signal for a particular channel is sent to you in that range Cable companies supply the Internet data as its own channel, a 6-MHz frequency range being used to send data to your cable modem Download speeds of cable modems have reached 10 Mbps but may differ with the different suppliers

FIGURE 8-13

FIGURE 8-14

One of the drawbacks of the cable modem is that you are sharing this bandwidth with your neighbors if they have subscribed to this Internet service as well If you have a neighbor that constantly downloads large amounts of data, you may nd that times are slow on the occasions when your neighbor uses the precious bandwidth Keep in mind that the Internet provider can simply provide the data through an additional channel to keep up with neighborhood demands if the provider chooses to do so! There is an advantage to cable modems and that is that unlike ADSL, you do not need to be within close proximity of a CO As long as you are receiving cable and your cable provider supplies Internet, you should be able to subscribe to high-speed Internet service Figure 8-15 displays a cable modem

How can you get high-speed Internet service if you are in a rural area that does not have access to high speed through ADSL or cable modems There is an option for getting high speed through the use of satellites, which provide download speeds as high as 500 Kbps Although not as quick as ADSL or cable modems, satellite can provide service to areas that are typically unserviceable and is much faster than the conventional 56-Kbps modem Satellite Internet uses a satellite dish that is about 2 feet high by 3 feet wide and uses two modems, one for downloads and one for uploads The modems are typically connected to the satellite dish through coaxial cable