DSL question 2 replies

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Spartan Advanced Member

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#1 15 years ago

I am looking into switching ISPs. I am wondering, what is dry line DSL? I had never heard the term before looking at some different plans.




[+Glasius+] Advanced Member

THE snowman

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#2 15 years ago

Im not even goanna try explaining on my own :p

History of Dry Line A "dry line", often called a "dry pair", came from the use of a copper pair from the local telephone company using security system providers. The dry line is basically an unbundled copper loop between the customer site and the telco central office that is not connected to the central office switch for service. The dry line only has DC current; hence, there is no signal on it. Additionally, the dry line is referenced as a non-loaded local loops that the ILEC put in the ground in order to provision services in the future. The most common example was to ensure that the ILEC would have a ready supply of "dry-copper" (unbundled loops) for home alarm type services.

Now, this practice went away after someone figured out how to use a "dry line" to provide data access by building their own network out of the phone company lines. In the past you can have a dry line at very low price for about $20.

Note that "dry line" doesn't necessarily translate into a usable line for xDSL transmission . The line may be bridged, the line may be "dirty copper", and the line may exceed distance requirements; that is to say that its quality is poor enough that it cannot handle high frequency signals that xDSL requires. It is best policy to test the line after it's been provisioned before installing any service on it. THE TERM "DRY LINE" IN xDSL ERA: Nowadays, the term "dry line" which is used in relation to xDSL deployment is referred as a "non-loaded local loop" between the customer site (CP) and the telco central office (CO) that is not connected to the central office switch for service. That would enable a xDSL provider (i.e. ISP, Corporation, etc.) to connect that loop to their DSLAM (Digital Subscriber Line Access Multiplexer) equipment, and hence offer xDSL service to their clients or employees. The term "non-loaded" or "non-loaded coils" means no passive low-pass filter for voice spectrum. With a low-pass filter, the loop is only used for voice signal only, the high frequency spectrum of signals (above 4Khz) will be filtered out, and the loop cannot be used for xDSL transmission. ORDERING xDSL LINES FROM TELCO: When ordering an xDSL line from a telephone company, make sure that you tell the the phone company that you use the line for data only or data and voice (i.e. using your existing telephone line). For data service only, you should tell the telco that you need a dry line or non-loaded line, it means that your xDSL loop doesn't need a "POTS splitter" (a POTS splitter is a lowpass filter that enables voice and xDSL data service on the same line simultaneously.) For both data and voice services, you should mention this requirement to the telco since it needs to install a POTS splitter at the xDSL line termination ends at both the telco central office and at the customer premises. At the central office the POTS splitter will split voice signal to the PSTN switch and data signal to a DSLAM device. At the customer premises the POTS splitter will split voice signal to a telephone handset and data signal to a xDSL modem.

NOTE: At the customer premises the POTS splitter is located at demarcation end (the boundary between outside wire taken care by telco, inside wire, under customers' responsibility.)




Spartan Advanced Member

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#3 15 years ago

:Puzzled:

Thanks.