2. External Cable Modems a small box that can provide a computer with an Internet connection through either usb or ethernet. most cable modems do come with USB ports installed as well as the usual Ethernet port
3. Internal Cable Modems Internal cable modems come in form of a PCI (Peripheral Component Interconnect) bus card for PC's Disadvantage: If cable modem is powered down just itself, computer would be powered down as well
4. Set Top Box Integrated Cable Modems Commonly used for services like interactive TV and Internet via your television Many companies use this type of cable modem to supply Internet access to your computer
5. Downstream/Upstream Downstream data is transmitted from the Internet towards the computer that requested it Upstream data is data that is sent or "uploaded" from a computer towards the Internet http://www.tvcinc.com/products/cm550.jpg
6. CATV Infrastructures Cable Access Television, sometimes known as Community Antenna Television Modems use CATV infrastructures that partly consist of HFC (Hybrid Fibre-Coax) http://www.microsens.pl/gifs_all/catv_node.gif
8. Tuner Connects to the CATV outlet Digital modulated signals and then forwards them towards the demodulator Can be attached to a diplexer, which enables the tuner to use a range of frequencies for both the downstream and upstream traffic
9. Demodulator Four main functions: QAM (Quadrature Amplitude Modulation) A/D converter (Analog to Digital) Error correction MPEG (Moving Picture Experts Group) synchronizer
10. Demodulator (Cont’d) QAM takes radio-frequency signal and changes it so the A/D converter can process it A/D converter converts signal into a digital signal of 0's and 1's Error correct module then compares the data received to a known standard, fixing errors in transmission MPEG synchronizer is then used to sequence and organise data groups into their correct order
11. Modulator Three main functions: To insert data that is ready for error correction QAM (Quadrature Amplitude Modulation) D/A conversion (digital to analog)
12. Modulator (Cont’d) AKA Burst modulator Converts digital data back into analog radio frequency signals so that they are ready for transmission
13. MAC (Media Access Control) Acts as the interface between parts of various network protocols Either the CPU of the cable modem or the CPU of the computer is used to take some pressure away from the MAC because of the complexity of its functions.
14. CPU (Central Processing Unit) The brain that controls all of the activity inside the cable modem itself www.novopc.com
