VitalPBX is free phone system based on the solid Linux and Asterisk platforms offering whole new level of user experience with offers fully responsive user interface and is easy to use, on any screen size. Downloads Manual here.
Sonata Switchboard is an application through which you can monitor in real time all the activity in your PBX.
Sonata Billing is a system through which you can rate all calls from your PBX. Allowing summary and detail reports to be generated.
Sonata Recording Management is a software through which you can manage the recordings of your PBX.
Sonata Communicator is a specialized Call Center Softphone, which includes options like, LogIn, LogOut, Pause, UnPausa, PickUp, etc.