VoIP-based PBX systems are better. They can have a limitless number of lines or extensions. The internet protocol also allows multimedia communications.
There are many ways to build an IP PBX/PABX system. The two most common are:Start from the ground up. The better and more affordable option for this case is to go for a hosted IP-based PBX system.
Upgrade existing legacy (landline) telephone systems. Companies can integrate existing phone numbers and hardware via PBX SIP Trunking.
Both methods use an internet connection to improve business telephony. They use ISDN (Integrated Services Digital Network) to process different types of data. Treat both as a data network as opposed to just voice.