A Class 4 PBX? What it is? In short, a class 4 PBX is the one that interconnects different PBX. It is very common that this class of PBX doesn't have contact with end-users. The perfect example of class 4 PBX is the carrier that sells IP telephony companies the DID's (origination) and outgoing gateways (termination). There are more differences between a 5 class and a 4 class PBX, my article about that covers it.
For the sake of this article, let's pretend everybody knows what is a class 4 and a class 5 PBX. Let's discuss FusionPBX. FusionPBX, out of the box brings let's say, 90% of all the needs a class-5 PBX needs: voicemail, IVR menus, time conditions, queues, and a lot of more features that are useless if all you want is a class 4 PBX.
Today I have published a very curious RPM. the FreeSWITCH Asterisk app_amd RPM 0.0.0 for CentOS 6, 7 and 8. This RPM claims to use the same technique of the Asterisk app_amd module.
I have tested with FreeSWITCH 1.10.5 and it seems to work very well. To find it, just do a yum search freeswitch-application-amd.
I have published today the SpanDSP 3.0.0 RPM for CentOS 6, 7 and 8. SpanDSP is a library of DSP functions for telephony, in the 8000 sample per the second world of E1s, T1s, and higher-order PCM channels. It contains low-level functions, such as basic filters. It also contains higher-level functions, such as cadenced supervisory tone detection, and a complete software FAX machine. The software has been designed to avoid intellectual property issues, using mature techniques where all relevant patents have expired. See the file DueDiligence for important information about these intellectual property issues.