Is it possible to run Asterisk without special hardware?
Yes, PSTN hardware like Digium cards or ISDN adapters is not a requirement. For some applications, like the conferencing application, you need hardware support to get timer support, but that’s possible in many ways. Asterisk works well as a VOIP and voicemail server with SIP, MGCP, IAX and H.323 support both with and without PSTN connectivity.