I used to work as a technician for a telephony company. My job consisteted in unpacking phones, connect them and label them. Around 2000, Enterprises started replacing their PBX with VoIP While setting up some of those VoIP telephones I met a guy who was happily setting up things in a black screen in the same server room. He explained me that he was using Asterisk PBX project and how he was setting up VoIP and an analog PBx line just using free software. (Our solution was Mitel wchih was a custom BSD distro) I was able to download it and customize it, this requires learning a lot of Linux commands, eventually completed my degree in CS and move from Latam to Silicon Valley to work in UC research