What are the Advantages of an IP PBX?

Compared to a conventional PBX, an IP PBX
-handles both voice and data,
-is cheaper since it requires only one network to install and maintain instead of two,
-reduces equipment costs (only IP based products; no voice products needed),
-reduces long distance charges for inter-branch office calls (by using the data network),
-is easier to provision (just plug in from wherever),
supports services such as unified messaging,
-is more flexible,
-is more scalable,
-makes it easier to provide new services, such as data and video collaboration,
-allows remote configuration (over the Web), and
-supports modular software upgrades, new technologies (new CPUs, etc.) are easy to incorporate.

What is an IP PBX?

A PBX is a customer premises telephone system that manages telephones in the enterprise and acts as the gateway to external voice networks. A switch/router directs incoming packets to the appropriate data network. Traditionally, two separate networks are required: one for voice and one for data.
Instead of two separate networks, one each for data and voice, only one network is needed if voice is packetized (Voice over IP) and sent over the data network.
An IP PBX is a combination of a switch/router and a PBX that handles Voice over IP (VoIP)

In an IP PBX, computers can be on a shared LAN that is connected to the IP PBX. Telephones, on the other hand, should be directly connected to the IP PBX. This avoids Quality of Service (QoS) issues that arise if both computers and telephones are on a shared LAN. In such a case, voice packets will have to compete with data packets for the shared LAN. Poor telephone voice quality will result if voice packets are not transmitted in a timely manner.

An IP PBX also acts as a gateway that provides voice connections (voice lines, T1s) to a LEC, a long distance company, etc. and data connections (cable, DSL, ISDN, E1) to a cable operator, a LEC, an ISP, etc. IP PBXs can be used bypass the circuit-switched telephone network by using the data network to connect to branch offices and other locations on the data network.

Using a single converged network that carries both voice (packetized) and data allows development of new services not typically available on the traditional network - for example, the use of one central directory across multiple locations and unified messaging.

An IP PBX replaces a traditional PBX. It can be used with

an IP phones (with a built-in DSP chip that converts voices to IP packets and vice versa),
a soft phone (software application on PCs that also converts voice to packets and vice versa), which is used with a headset or a handset,
existing phones along adapters that packetize voice, and
standard phones connected to PCs (PCs acts as the adapters).

As in case of computing devices, IP addresses are automatically assigned to phones as they connect to the system. This means that a telephone can be moved from one location on the network to another. The telephone number remains the same as it associated with the phone.

VoIP packets can be packetized using protocols such as G.711 or G.723:

G.711: an encoding standard for packetized voice; uses 64 kbs and can communicate with other G.711 devices.
G.723: an encoding standard for packetized voice that does compression; uses 6.4 kbs and can communicate with other G.723 devices but not G711 devices.

How Does VoIP Work?

There are phones practically everywhere and even a typical household may have one for each member of the family. Nowadays, as computers are beginning to take the role as tools to speak to another person, one could wonder how does VoIP work.
VoIP, also known as voice over internet protocol, is a standard of being able to communicate using sound signals using the internet rather than the classic telephone networks. It allows even greater distances to be reached, as all it takes is a computer and software to utilize.
For VoIP, it would definitely replace conventional phone lines in the future, yet how VoIP works would depend on two types of things.
Computers with messenger software like Skype can be used to call anyone's computer who uses the same software. This can be considered as free since a link can be established directly through that software. If calling to a landline or cellphone, there are certain rates apply, and they're usually cheaper in comparison from the regular carriers.
There's also a special phone that utilizes VoIP works the same and even has some special options like caller ID included. These phones work like an ordinary telephone, only being able to call anyone in the world without added costs and if they also have VoIP. These phones are usually found in businesses that specialize in customer care and the like.
There are several answers on how does VoIP works, yet the technicality of it can always be simplified as it is during the invention of the telephone.
By Elija James