The Mac mini is a very tiny and rugged PC, making it a great small-office PBX.
When Apple introduced the Mac mini, most onlookers were pleased to see a smaller machine with plenty of muscle—enough to handle a few dozen VoIP phone calls at a time—even though most observers didn't have VoIP in mind for it. At less than $500, the mini is great for the cost-conscious, and for those who don't trust the likes of Windows in a real-time application like IP telephony, a Mac provides a secure, friendly alternative. Of course, there are comparably equipped "small" PCs, but none with the tiny (two inches tall, and six by six inches square) form factor of the Mac mini. So, if you need a space-conscious, cheap VoIP server, you need look no further than the mini.
Would you rather use an Xserve with this hack? Great idea! The Xserve has faster processors and a RAID hard-drive array. This means high-performance PBX action. It also has an extra Ethernet interface and a swappable power supply, making it better in mission-critical situations than the mini.
But, since the Mac mini has no card slots (and since multichannel PCI telephony drivers are not available for OS X), attaching analog phones and phone lines to a Mac mini isn't the same as in a traditional, PCI-equipped server chassis, where you can snap foreign exchange office/foreign exchange station (FXO/FXS) cards into place to connect phone lines. This is where VoIP comes in handy. Just because the Mac mini can't connect ...