To use VoIP you need apart from a broadband Internet connection (DSL, cable, etc., vendor-independent) appropriate hardware or software.
In terms of hardware, there are different solutions. The simplest is an IP phone that is connected to your home or corporate network. These phones can be equipped and configured with the access of the VoIP provider using web browser in order to register on their system. A further solution is for example the widespread Fritz box fon, which is a complete PBX. To their existing analogue or ISDN phones can already be connected and used. Since they also (including DSL modem) is used as a network router, the use of this particular type devices in the home and offers are also configurable via a web browser.
For professional use, however, the more traditional telephone systems are used which were developed specifically for VoIP telephony, but hardly different from their known from the fixed network business systems from the basic concept. Also here is the actual telephone system as the core of the rule, then System phones operate.
As a software solutions called softphone programs are installed on a PC or notebook and operated with a headset to use. The configuration is usually somewhat larger, since the interaction between softphone and headset components of the PC-/Notebook or their settings (sound card) is affected qualitatively. For this, the investment cost is very low as most softphones are available for free on the Internet and thereby makes only one headset on the cost side noticeable.
But also for professional use software-based solutions have become established. A program is installed on a PC or server, which then transforms this into a full telephone system. Behind then both IP phones and softphones can be used, which will not be described as above register directly with the VoIP provider, but on this software-based phone system. Everything else will then take the equipment itself
So there are a variety of solutions with VoIP telephony is possible. Therefore dus.net GmbH pays close attention to their services always RFC compliant (see also SIP) to hold, so that no matter which solution you use, always smooth VoIP telephony is possible. Assuming your used hardware or software solution also does this, which should be the case in general.