Dial-Up & DSL

There are two fundamental differences between Dial-Up and DSL service and modems:

Connection method –

Dial-Up requires a dedicated line and a new connection created for every session.

DSL, once initially set up, is always on, and allows for concurrent use of the telephone.

Speed –

DSL can be 15 to 100 times faster than dial-up.

But to understand a bit deeper, we need to discuss the general concept of communication between computers, which is accomplished by using modems.

Computers use digital “1s and 0s” as their internal “language”. A modem is a device connected to a computer that modulates and demodulates a signal to encode its information during transmission (thus the name modem – modulate / demodulate). A modem can transmit computer data over a telephone line. Just as the telephone line is used to transmit sound from one location to another, it can also be used to transmit computer data. A modem converts those “1s and 0s” into sounds and transmits them over telephone lines to another modem on the receiving end, which converts those sounds back into “1s and 0s” to be again recognizable to computers.

Dial-Up (analog-type) modems: These are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or "bps". A modem will transmit a bandwidth of 64 kilobits (thousands of bits) per seconds (kbit/s, kbs, or just 64k) over a telephone line. They usually operate, though, at speeds ranging from about 28.8K to approximately 45K. Even 56K modems do not transfer data at a full 56 Kbps.

DSL Modems: The same telephone line on which a dial-up modem transmits its signals, when handled by DSL technology, can handle several megabits (millions of bits) per second (mb/s or m). DSL is a type of technology that allows access to the Internet at high speeds or along a “wide” “path” on which data travels, allowing greater “bandwidth”, which, in turn, allows more information carried per second. Thus, DSL is referred to as broadband, relative to Dial-Up technology.

Since DSL modems use higher frequencies than that used to service the phone or fax, DSL is able to use the telephone line without disrupting the other service. DSL effectively turns your existing copper phone line into a multi-channel delivery system. One channel transmits standard telephone services like voice or fax. Other channels carry high-speed, DSL computer data. It is recommended, though, to use a special filter on your telephone lines, to ensure that no stray “noise” between the “channels” affects the other’s usage.

The download speed of DSL (time it takes for information from elsewhere to get to your computer), typically ranges from 640k (640,000 bits per second) to ~3m (or 3mb/s, which is 3 megabits, or 3 meg, or 3,000,000 bits) per second, depending on the DSL technology and service level implemented. Upload speed (time it take to send information from your computer) is typically slower than download speed, which is of less importance, since generally, most of the data traffic is incoming, not outgoing.

This chart describes some differences between DSL and Dial-Up.