Most of you, who have reached this article, are basically trying to find out the difference between ADSL and DSL modem. We need to understand some basic aspects before going into the details of the difference between the two (if any).
What is a DSL Modem?
A modem is a device that is used for modulation and demodulation of the data that is transmitted or received, respectively. Now, what does a voiceband modem do when connecting to the Internet? Well, it converts the digital data of the computer into sound signals and transmits them through the telephone channel. Similarly, it converts the voice signals that it receives, into digital data. This is how a simple voiceband modem works. For a while, such modems were used to connect to the Internet. The problem with them, was that they were very slow in browsing.
A voiceband modem, when connected to an ordinary copper telephone cable, can only use a frequency range of 3400 Hz from the available bandwidth. But 56,000 bits per second, is the bandwidth allowed for communication through the lines. So high speed Internet access or LAN access, viewing videos etc. was not possible, while using a voiceband modem. Besides, when the voiceband modem was connected to the telephone line for data transfer, it was not possible to use the telephone at the same time. This gave rise to the need of a different modem, to access the network at a high speed and at the same time, allow telephone lines to be used simultaneously.
Thus, the DSL (Digital Subscriber Line) came into existence. This technology uses the same telephone lines, this time, made of copper, to carry data using a very high bandwidth. This not only increased the speed of transmission but the telephone line can be used to make calls, while connected to the network, using the same cable. The DSL modem allows data to be transmitted and received at a higher speed. All that is required is that a DSL modem is connected to the user's terminal and a similar DSL modem is connected at the service provider's terminal.
What is an ADSL Modem?
An ADSL (Asymmetric Digital Subscriber Line) is one of the types of DSL broadband communication technology. Hence, an ADSL modem is a type of DSL modem. A downstream speed of 1.5 to 9 MBPS is possible and an upstream speed of 16 to 640 KBPS is possible, when an ADSL modem is used. Now, what is the difference between ADSL and DSL? Well DSL modems can be of two types, SDSL (Symmetric Digital Subscriber Line) and ADSL.
The difference comes when we use the word ADSL, which means that data is sent and received at different speeds. It means that your modem sends data to your service provider at one speed and the downstream data, the data that you receive from the service provider is at a different speed. Hence, the word asymmetric has its significance in ADSL. The service in general is tiered, hence you pay different rates for different speeds.
So basically, there is no real difference between DSL and ADSL, one is a type of the other. Most of the time when we use the word DSL, we generally refer to ADSL modems, but in certain cases, it can refer to SDSL modems. The difference between the two is that an ADSL modem can send and receive data at different speeds while a SDSL modem can send and receive data using one speed only.