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Loop Class
Description
Rate
Class I
6000ft, 26 gauge
6.176 Mbps
Class II
8000ft, 26 gauge
4.632 Mbps
Class III
12000 ft, 24 gauge
3.088 Mbps
Class IV
18000 ft, 26 gauge
1.544 Mbps
Key Points
A technology that converts existing twisted pair phone line into a high-speed transmission path for
data communications
POTS operates in the 300 – 3400 Hz frequency band
Simply stated, ADSL is an access technology for services that require high-speed digital transmission.
It only supplies access to the Telco’s high-speed network. Where your data goes from there is
determined by the SERVICE you subscribe to.
To achieve high speed though, ADSL modems use all the available bandwidth inherent in twisted pair
copper wires, while a dial up modem will stay within the small band of frequencies regular phone
lines use.
Divided into two unequal size bands (Asymmetric)
Figure 71: Upstream and Downstream
How it Works?
The fundamental of ADSL uses Quadrature Amplitude Modulation (QAM)
Four points (constellation) in each quadrant
Uses sine or cosine wave to transmit data as it hits each constellation
The sine and cosine waves varies in phase and amplitude
Figure 72: Quadrature Amplitude Modulation