What does DSL Stand for?

With a classic DSL connection, the DSL modem acts as an intermediary between the telephone connection and the end devices such as telephones or PCs. In modern DSL technology, the DSL modem is usually no longer an independent device, but is integrated into the DSL hardware.

  • A DSL modem is a communication device that can receive and forward digital signals.
  • A DSL modem cannot be combined with all types of connection.
  • The existing telephone connection (analog, ISDN or Voice over IP) determines how the DSL modem is connected correctly.
  • Modern DSL hardware are routers that take on the functions of a modem, WLAN receiver, connection to a telephone system and media server.

What are the tasks of a DSL modem and what is it used for?

A DSL modem is both sender and receiver. The term is made up of “digital subscriber line” (DSL, digital subscriber line by abbreviationfinder) as well as “modulator” and “demodulator” for the word modem . The DSL modem separates data from the usual telephone signal. This requires a so-called splitter, which divides the incoming signals into analog (telephone) and digital (data). The DSL modem therefore has two tasks:

  • Modulation: Conversion of useful signals into tones for transmission over long distances
  • Demodulation: Conversion of the incoming carrier signals back into analog and digital values

Different frequency ranges increase the transmission speed

Data exchange between the DSL modem and another digital device is possible over long distances. To ensure fast data transmission, a higher frequency range is used than for voice transmission in telephony.

What should you watch out for when connecting a DSL modem?

A DSL modem is always connected to the receiving device (computer, laptop, etc.) via a LAN cable ( Ethernet cable). Different versions support different technologies when connecting. This also means that different transmission speeds are possible. Basically, the manufacturers deliver the DSL modems with detailed installation instructions. Work through this step by step to ensure that your DSL modem functions properly. If you want to send data to several end devices, put a splitter in front of the modem.

Not all connection types are suitable for a DSL modem

If you use your Internet access from a cable TV provider , you do not need a conventional DSL modem. The respective providers provide their own devices for access to the network. A commercially available DSL modem is also unsuitable for fiber optic connections (VDSL). A special fiber optic modem is generally integrated in the router.

Why is a VDSL modem less useful than a VDSL router?

VDSL is a special DSL technology that offers higher transmission rates. While DSL has a bandwidth of up to 16 Mbit / per second in the downstream, VDSL offers bandwidths of up to 100 Mbit. VDSL is usually used where several digital devices need high-speed access to the Internet at the same time. A VDSL modem, which is rarely available in stores, only allows access to one digital terminal. VDSL routers are therefore used for VDSL connections, which provide suitable Internet connections as a connection for the telephone system and at the same time for PCs, laptops or smartphones.

Analog, ISDN or Voice over IP: Everything is possible with the right DSL hardware

If you have an analogue or an ISDN connection, when buying a DSL modem, make sure that it has an integrated splitter. So you only have to connect one device. The splitter is necessary because both the data and the telephone signal are transmitted over a telephone line. These signals must be separated again on the receiver side by a DSL splitter. With Voice-over-IP technology , voice information is sent over an Internet connection. Here, as a rule, neither splitters nor DSL modems are necessary because these devices are already integrated in standard routers.

Why does the combination of router and DSL modem make sense?

If your DSL modem is a simple model without a router function, an online function is only possible for a single computer without the corresponding additional devices. This cannot be changed even with additional LAN access. You can then connect several devices, but a simple DSL modem without router function only provides a connection to the Internet for a PC. If several end devices are to have access to the network at the same time, an external router or something similar is necessary. This is a very common variant, especially with wired connections.

The advantages of modern DSL hardware

  • WLAN routers with an integrated DSL modem and splitter provide Internet connections via the internal radio network.
  • They are very suitable if you want to set up an in- house network.
  • These routers are also suitable as media servers. Stream music or films from the Internet and transfer them to your (modern) television.

This gives you perfect connections to your telephone system and various receiving devices.


A DSL modem is essential for connecting to the Internet. You have the choice between a simple modem with an upstream splitter (two devices) or modern DSL hardware that combines the modem, splitter, router and WLAN receiver.