While it won't be anything to brag about, this basic PBX that you will build from Asterisk will help you learn the fundamentals of configuring Asterisk. For this exercise, we're going to assume that you have access to two phones which speak the SIP voice-over-IP protocol. There are a wide variety of SIP phones available in many different shapes and sizes, and if your budget doesn't allow for you to buy phones, feel free to use a free soft phone. Soft phones are simply computer programs which run on your computer and emulate a real phone, and communicate with other devices across your network, just like a real voice-over-IP phone would.