PABX stands for Private Automatic Branch Exchange. It is a PBX that switches calls automatically, with no human operator at a switchboard. In everyday use, PABX and PBX now mean the same thing.
Like the PBX, the PABX has largely moved to the cloud. The automatic routing it pioneered is now table stakes, layered with IVR menus and AI answering.
Frontdesk gives you a business number answered by an AI receptionist that picks up every call, qualifies the caller, books the appointment, and logs the whole conversation to your CRM.