The 3CX software can be downloaded as the 3CX Free Edition which will provide connectivity for unlimited extensions and enable 8 simultaneous calls and has reduced functionality compared to the 3CX Enterprise Edition.
The 3CX Free Edition is a great way of trying out the PBX as long as you are prepared to invest some time and also invest in high quality VoIP Appliances such as the Snom IP Phones and Patton VoIP Gateways. If you use the 3CX with low quality VoIP Hardware and low cost SIP Call providers you may not see the advantages and true quality a VoIP PBX can offer to the small to medium enterprise.
The 3CX Free Edition can easily be upgraded to the 3CX Enterprise addition, by purchasing a software key to unlock the extra features. Upgrading to the 3CX Enterpise Edition and the various support packages available will enable your business to benefit from a leading edge Phone System, with real support and valuable spftware upgrades to keep your system providing the quality you would expect for your business.