This 'hands-on' paper describes how to build a VoIP telephony system. The paper starts with an introduction to the essentials of telephony over the Internet (Sections 2 and 3). For those who want to put theory into practice, the two following sections cover how to build a PBX including assembling the hardware (Section 4) and installing the software (Section 5). Instead of listing all possible commands and endless configuration options, the authors have selected three practical scenarios as basic examples with the clear goal of getting the system up and running. The three scenarios are: • Private telephony in a rural community (Section 6) • Connecting the local telephone network to the PSTN (Section 7) • Interconnecting two remote communities (Section 8)