Digital Subscriber Line Access Multiplexer


What is a DSLAM?
A DSLAM device is generally used by the central office of telephony service provider. This sophisticated network device gathers signals from the DSL connections of numerous customers and then uses multiplexing to upload them onto a speedy backbone line. Phone companies can offer home subscribers and businesses fastest DSL connection speeds using a DSLAM.
What purpose does a DSLAM serve exactly?
A DSLAM is the primary equipment that allows the completion of a DSL connection. It is a flexible device that supports numerous sorts of DSL in a central office. The DSLAM determines major differences between the internet connections established through cable modems and through ADSL. Cable modems commonly share a single network loop that is spread out around a neighborhood. This means the addition of more users will inevitably lower overall performance of the network. In such connections, a DSLAM provides an independent connection from every subscriber. This means that an addition of new users to the network will barely affect performance.
What benefits does a DSLAM offer the end-user?
Establishing an internet connection using a DSLAM offers a wide range of benefits to the end user. DSLAMs allow internet service subscribers internet connections at incredible speeds. The speed offered by DSLAM is unparalleled, restricted only by two factors:

  1.  The processing capacity of the computer equipment of the internet service subscriber
  2.  The measure of bandwidth that is devoted to DSL by the provider

With the connection between the user and the DSLAM established, a wide range of online tasks can be performed with absolute ease given the incredible speed offered by the connection. DSLAM allows for faster mailing, blogging and shopping.

What are the most common uses of DSLAM?
A handful of businesses install DSLAM on the roof of their property simply to optimize the internet connection and make it more efficient. Hotels commonly use DSLAM as a critical component of their internal communications network other than using it for high-speed internet connection.
Housing DSL services in cities use multiple DSLAM that are strategically distributed around the perimeter of the city typically at switching stations. This allows ISP servers to increase the total number of multiplexer as the population of subscribers increases.

ADSL Low Pass Filter

ADSL Low Pass Filter

What is a Low Pass Filter?

In electrical engineering, “break frequency” is that point in the frequency response of a system at which the flow of energy starts to decrease instead of passing through. Low-pass filters, as their name suggests, are electronic filters that regulate the amplitude of signals decreasing frequencies that are above the break frequency. They are an important and widely used tool in ADSL services.

Why are Low Pass Filters Needed?

Originally, telephone wires were designed to share “Speech” between two destinations using a low band of frequencies (300Hz to 3400Hz). To ensure fast data traffic, ADSL uses a higher band of frequencies (25 kHz to 1.1 MHz). ADSL systems can be integrated into the same telephone line and can share the same wire at a time for data transfer because they both operate at different frequencies. However, the electronics hardware associated with a conventional telephone is usually not adaptive to high frequency signals of ADSL. This can lead to interference in the reception of the telephone line where high-frequency signals of ADSL can be recognized as resonating sounds and noise that cause annoyance and disturbance. This is where a low pass filter is used to separate two different components from the telephone line.

How do I Install a Low Pass Filter?

An ADSL Low Pass Filter is a small plastic box with a lead that goes into the telephone socket. It has one output each for the telephone and the ADSL Modem (some low pass filters have just a single telephone output). Once you are done connecting all the wires in their respective sockets, the ADSL filter chooses different bands of frequencies for the phone and the ADSL modem. It then sends the ideal band to the respective sockets. For optimum performance, it is essential that you separate all your telephony equipment with the ADSL filter. When installing an ADSL filter:

  • Make sure your phone and equipment is passing through a filter
  • Make sure that the ADSL signal passes through a single Filter

Make sure you use the same Filter for all phones

ADSL Loop Extender

data signal amplifiers

What are ADSL Loop Extenders?

As its name suggests, an ADSL Loop Extender is a signal amplifier that DSL service providers position between their internet server office and the location of their subscribers. A loop extender serves two primary purposes:

  1. extending the distance that the DSL internet connection can reach
  2. increasing the overall capacity of the DSL connection channel

Until the invention of remote DSLAMs and ADSL loop extenders, the distance of ADSL internet connections from their server location was restricted to roughly 5 to 10 kilometers (3 to 6 miles). However, ADSL Loop Extenders serve the purpose of signal amplifiers, optimizing signal strength so that it can travel farther. Some DSL service providing companies using ADSL Loop Extenders promise high speed internet connections to subscribers as far as 10 miles from their server location.

What benefits do ADSL Loop Extenders really provide?

Outside impairment and obstructions are usually the causative factor of degradation and possible failure of ADSL performance. ADSL Loop Extender allow DSL servers to provide high-speed internet access to remote areas with tested loops that are an amalgamation of refined installation techniques and strong transmission technologies. They maintain a steady connection speed even in conditions that are not conducive of perfect internet speed.

ADSL Loop Extenders also triumph over random impairments and impediments whether in existing connections or new ones. Noisy reception, spectral interference and disturbance are just some of the common problems that they are known to eliminate. Here is a short list of the other benefits that an ADSL Loop Extender offers:

  • Many ADSL companies have been quick to use DSL Loop Extenders for the fact that they literally double the number of customers that are accessible by a single DSL internet server location due to increased signal strength.
  • Another great benefit of ADSL Loop Extenders is that they provide a greater bandwidth. It is common for these devices to increase bandwidth by 2 to 10 times.
  • Minimum signal interference and disturbance means minimum loss of customers due to unavailability of internet service.
  • DSL Loop Extenders also provide extensive protection against instances of over-voltage that can cause serious damage to hardware.

ADSL Installation Problems

Slow ADSL Internet

An ADSL connection can go wrong because of a wide range of reasons – the splitter/filter, the modem/router or even your phone jack! Here are some of the most frequently asked questions (along with their answers) that DSL internet providers get from subscribers of their service.

Why has my broadband stopped working all of a sudden?
In case your ADSL connection suddenly terminates unannounced, there is a high likelihood that the modem is the cause of this. Check by:

  • Switching the modem OFF and then ON again
  • Log in using the username and password
  • Check line and cable connections
  • Try to connect the modem directly to the telephone jack rather than through the filter (to check if the filter is faulty)
  • In the absence of a dedicated ADSL filter, the landline phone is the most common culprit
  • Try replacing the modem with another one

Modem issues sometimes require extra care and it is best to reconfigure them or reset them to factory settings.

Why is my DSL connection so slow?

The speed of a DSL connection is influenced by a range of factors. When you are experiencing slower than usual speeds, check if:

  • Your house is situated at a considerable distance from the server location
  • Your monthly/quarterly quota has been used up
  • Your telephone lines are properly connected to the ports
  • Your modem is not the culprit
  • Your DSL connection’s security has not been compromised by a hacker

Why does my DSL connection end every time my telephone rings?
Using your landline without installing a filter on each telephone in your house is bound to cause interruptions in both the telephone and DSL service. In such cases, interruptions in telephone lines, dropped calls, noise and sudden termination of ADSL connections is common. Installing filters effectively takes care of this problem.

What do I do when I have figured that it is not the modem?
If you have thoroughly scanned the perimeter of your house and are certain that all the hardware is functioning satisfactorily, then the most probable explanation is that you are having problems with internal wiring. Also, check with your service provider to confirm that the problem is not from their end.

My ADSL is slow or stops when it rains
This usually happens when the insulation of copper wires has been compromised due to incessant soaking in the rain. Under such circumstances, the normal speed of the connection is restored some time after it has stopped raining. Reboot the modem if problem persists.

ADSL Modems

ADSL Modem

What is an ADSL Modem?

An ADSL (Asymmetric Digital Subscriber Line) modem, also called an ADSL router, is used to establish a connection between a computer station and an internet server. DSL modems ensure faster speeds on the internet because they are tailor-made for DSL connections which allow faster internet speeds as compared to a dial-up connection. DSL Modems allow users access to the telephone line while also providing them an internet connection.

Is an ADSL modem different from a Dial-up Modem?

Although the service that an ADSL modem provides is largely similar to that of a dial-up connection, the major differences between the two are:

ü  In the internet speed that they allow – An ADSL provides higher throughput and latency when compared to a dial-up connection. This means that with a higher capacity for data transfers, it offers higher speed of internet connection.

ü  In the setup/technological make-up – Dial-up modem is an internal connection and needs to be “installed” inside a dedicated computer terminal. On the other hand, an ADSL modem  is generally connected to the computer externally through a USB port.

Can I connect TWO computers using an ADSL modem?

You can also use an ADSL modems to establish a network connection between more than two computers (including the server). In such an instance, an Ethernet DSL modem allows a high-speed connection whether it is shared between two computers or more. However, in order to allow networking, the ADSL modem needs to have the capacity to translate network address.

Where can I get the best ADSL Modem?

DSL modems are a common hardware and are readily available in most electronics markets, computer hardware stores and even departmental stores. You can also buy ADSL modems cheaply online via Amazon. While most ADSL Modems are built to last long, something which is obvious considering that they are sedentary hardware devices, researching can nevertheless assure that the best warranty is provided to you in case of a hardware defect. ADSL service providing companies often provide their own DSL modems free of charge.

What does the ADSL modem packaging usually include?

More often than usual, the packaging of ADSL modems includes all the necessary cables apart from the power supply adapter and low pass filters.

ADSL Speed Test

ADSL Speed Test

What is throughput?

Throughput is the speed at which a network or computer transfers data at a particular point in time. It is an effective way of checking the optimum capacity and speed of a DSL connection. Throughput is measured in bits per second (bit/s). Assuming that it takes a bike, a car, and a bus the same amount of time to travel from point A to point B, the bus will be able to carry more data (passengers in this case) because it has a greater capacity.

In the same way, Throughput is the capacity of data that can be transferred within a particular amount of time such as 4MB or 14MB. DSL connections that promise better throughput have the capacity to offer larger volumes of data in a particular amount of time. Generally, DSL connections can transfer 30 megabits of information from one computer to another in one second and have a throughput of 30 Mb respectively.

However, Latency is as important in determining the speed of the DSL connection as throughput. Taking the afore-mentioned example further, it is of little benefit to the internet user if the bus takes an entire day to transfer data from A to B. The same way, Latency measures the time it takes to deliver data a prescribed amount of data from the serving entity to the client. The unit of latency is time.

How do I check my internet speed?

Checking the speed of your DSL connection is not rocket science. You can simply measure the speed by checking how long it takes to download files. If you have a 4MB connection then downloading a 7MB MP3 file shouldn’t take more than 14 seconds. In addition, a DSL connection generally takes 10 minutes to download a television show (350MB) and 20 minutes to download a movie (700MB).

For a more official assessment on your DSL connection speed, you can try one of the online speed tests. The internet is a wonderful resource for evaluating the download speed, upload speed, throughput and latency of your DSL connection. Online speed tests also provide other useful details about DSL connections such as the throughput and the latency. Here is what you need to keep in mind when trying the online speed test:

ü  You should select the closest server location. For obvious reasons, a remote server will take more time to transfer data and will have a higher latency.

ü  You should download a sample file from the selected server. This process gives you a better idea of the upload/download speed of your DSL connection.

DSL Splitter

Dlink DSL Splitter

What is a DSL filter?

It is a device fixed between your telephone line and telephones, fax machines, computer modems and other analog modems. The type of telephone line it connects to is POTS (plain old telephone service).

Why is a DSL splitter necessary?

If a DSL Splitter is not present between two or more devices operating through the same telephone line, your DSL connection can experience interference which can lead to further problems.

How do DSL Splitters work?

A central splitter is the DSL splitter that is installed into the telephone line. A splitter has two filters that separate low-frequency signals and high-frequency ones. It uses a low-pass filter in order to avoid the interference of high-frequency ADSL signals. Additionally, a dedicated high-pass filter serves as a barrier that eliminates the POTS (Plain Old Telephone Service) signals present in the ADSL line. It is common for DSL providers to install a central splitter before making the primary telephone point.

How do I install a DSL Splitter myself?

Installing a DSL Splitter is a fairly simple task and is definitely NOT rocket science. All you need is to know where to connect all the wires. If you wish to keep your modem/router in a specific location while being able to use the DSL connection on multiple computers in other rooms at the same time, you should:

  1. Use the blue/white wire for the voice jacks. One end of the blue/white wire should be plugged into the “Network” location in the splitter while the other is connected to the Network Interface.
  2. Remember that the 2 remaining locations are “Voice” and “Data”. Use a jumper wire to connect the remaining blue/white wire on the panel with the “Voice” posts.
  3. Take a jumper from the “Data” posts. Remember to connect a jack to it nearest to where you will place your modem.
  4. Connect the “Data” jack with the modem. Also remember that the Ethernet cord goes into the Ethernet port.
  5. Connect the router/switch to the other end. Lastly, make sure that you wire in the patch cords from the router/switch to the dedicated data ports in the panel.

Why unlimited ADSL?

Unlimited ADSL

Unlimited ADSL offers consumers a number of benefits including

  • Download or surf as much as you like you have no limit of hours
  • Most have no excess usage fees on downloads
  • Most offer no throttling or shaping of internet speed
  • It’s available in regional locations
  • Don’t worry about using your downloads during peak times
  • You can watch most free-to-air tv channels online
  • Some offer unique digital TV content free online