PBX vs PABX
The first thing you would notice about PBX, which stands for Private Branch Exchange, and PABX, which stands for Private Automatic Branch Exchange, is the presence of the word automatic. This gives a hint on how the two differ from each other. Basically, a PABX is just a type of PBX that is automated. There are also other types of PBX’s like PMBX and EPABX but we won’t go into that.
PBX is a very old concept in telephony that started long before electronics were involved in it. In its earliest days, a PBX is a room where switchboard operators connect calls from one end to another by manually plugging wires to complete the circuit. As technology evolved, new improvements were added to the PBX. One major advance is the advent of electronic switching. This allowed the system to be automated and the involvement of humans virtually eliminated. This prompted the need to have a new term to distinguish the new system from the old one. Thus, the term PABX was created for the new automated system while PMBX was used to identify the older manual system.
Nowadays, PBXs have evolved much further from the PABX and PMBX systems used decades ago. And since all PBXs are now automated, there is no longer any need to differentiate between the automated and manual systems. Because of this, the terms PABX and PBX are used interchangeably as they basically point to the same system.
PBXs have even added new features that were virtually non-existent during its advent. Things like call conferencing, call waiting, automatic ringback, and many more features now come as standard in a typical PBX. PBX systems are also capable of including cellular phones aside from the traditional wired lines. More importantly, many modern PBX systems are now able to perform IP based telephony. This is a packet based network (i.e. the internet) and is very dissimilar from the circuit switched networks of ordinary phone networks. IP based telephony, also known as VoIP, presents several advantages to PBX systems as it can greatly reduce costs by maximizing the efficiency of the available bandwidth.
Summary:
1.PABX is just one type of PBX
2.Nowadays PABX and PBX usually mean the same thing