Router

A Virtual Private Network, abbreviated as VPN, makes it possible to build secure private connections over public access network infrastructures. Today VPNs are usually based on Internet Protocol (IP) and use the public Internet to establish the connection. Depending on the type and use, a VPN can be created between two terminals (computers), between a computer and a network or between two networks. In the latter case, the VPN connection of two routers is realised. The data transmitted within a VPN is encrypted and protected against unauthorised access in a sort of tunnel through the Internet. Encryption standards such as IPSec or TLS/SSL are used. Many private Internet routers now have VPN functionality and allow laptops, smart phones or tablets that are being used elsewhere to create a secure connection to the home network. This technology makes it possible, for example, to protect data transmitted to and from a public hotspot to a home network and to access the Internet from there.

In telecommunications technology, the abbreviation ISDN stands for the technical term "Integrated Services Digital Network" and refers to a digital standard for telephone networks. As the name implies, various types of communication services can be transmitted through this kind of network. In addition to voice calls, ISDN allows packet-switched or circuit-switched data transmission and fax transmission.

In some countries, ISDN technology has taken over from analogue telephone networks, integrating all types of services into a common network for the first time. This digitisation has also enabled digital ISDN phone lines to be made available to end users.

In comparison to an analogue connection, an ISDN subscriber line offers a whole range of advantages. The basic ISDN line allows multiple phones or communication devices, with different numbers (MSNs), to operate and use two parallel connections simultaneously. In addition, the ISDN connection also offers higher data transfer rates to an analogue connection using a modem, for example, when accessing the Internet.

To utilise the ISDN line, end users need special ISDN-capable phones or faxes. The use of so-called A/B converters, linking analogue devices to a digital connection, is common. Meanwhile, other techniques such as DSL or cable connections are used for connecting to the internet. Nowadays, phone technology is evolving away from ISDN and towards IP telephony via Voice over IP (VoIP).