Fiber Optic Wiki

A DSL connection can be deployed over existing cable

December 15, 2011

Because DSL operates above the 3.4 kHz voice limit, it cannot pass through a load coil. Load coils are, in essence, filters that block out any non-voice frequency. They are commonly set at regular intervals in lines placed only for POTS service. A DSL signal cannot pass through a properly installed and working load coil, while voice service cannot be maintained past a certain distance without such coils.

A Naked DSL

December 15, 2011

A naked DSL (a.k.a. standalone or dry loop DSL) is a way of providing DSL services without a PSTN (analogue telephony) service. It is useful when the customer does not need the traditional telephony voice service because voice service is received either on top of the DSL services (usually Voice over IP) or through another network (mobile telephony).

Typical setup of DSL transceiver

December 15, 2011

On the customer side, the DSL Transceiver, or ATU-R, or more commonly known as a DSL modem, is hooked up to a phone line. The telephone company (telco) connects the other end of the line to a DSLAM, which concentrates a large number of individual DSL connections into a single box.

Modern DSL gateways

December 15, 2011

Modern DSL gateways have more functionality and usually go through an initialization procedure very similar to a PC boot up. The system image is loaded from the flash memory; the system boots, synchronizes the DSL connection and establishes the IP connection between the local network and the service provider, using protocols such as DHCP or PPPoE. The system image can usually be updated to correct bugs, or to add new functionality.

There are two ISDN implementations

December 14, 2011

In ISDN, there are two types of channels, B (for "bearer") and D (for "data"). B channels are used for data (which may include voice), and D channels are intended for signaling and control (but can also be used for data).

Some of the services envisioned as being delivered over ISDN

December 14, 2011

Among the kinds of data that can be moved over the 64 kbit/s channels are pulse-code modulated voice calls, providing access to the traditional voice PSTN. This information can be passed between the network and the user end-point at call set-up time. In North America, ISDN is now used mostly as an alternative to analog connections, most commonly for Internet access.

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