What is a PBX?

PBX (Private Branch eXchange) is a privately owned telephone switching system for handling multiple telephone lines without having to pay the phone company to lease each line separately.

Normally a telephone line is connected to the phone company’s local Central Office through “a trunk.” The Central Office is responsible for routing incoming and outgoing calls. It also provides other services like voice mail, call forwarding, caller ID and other features.

Companies use a PBX for connecting all their internal phones to an external line. This way, they can lease only one line and have many people using it, with each one having a phone at the desk with different number. The number is not in the same format as a phone number though, as it depends on the internal numbering. Inside a PBX, you only need to dial three-digit or four-digit numbers/extensions to make a call to another phone in the network.

Types of PBX Systems

Traditional PBX

A PBX is a privately owned phone system for handling multiple phone lines and routing calls. Depending on the services you need, it can be costly or rather cheap. Typical features include call forwarding, voice mail, caller ID, and conferencing. These systems are being used less because they are harder to install and need to be connected to a land line. However, they remain a very stable option and are favored by medium to large-sized businesses.

Hosted/Virtual PBX phone system

A Hosted PBX is a virtual telephone system where, instead of having all your telephone hardware in the office, your hardware is provided by a system hosting company and you connect to the system via a network connection.

Hosted PBX telephone systems have some advantages over purchasing a standard PBX or VOIP system for your office.

  • Reduced Hardware Costs
  • Reduced Upgrade Costs
  • Always Having The Latest Features
  • Cheaper Calls
  • Easy System Management

Diagram of a Typical Hosted PBX Configuration


This hosted phone system brings the benefits of both worlds together. Costs are greatly reduced since there is no extra hardware to install. Phones can be connected to a computer port, rather than deal with wires. Like a virtual PBX, you can manage your system online. Just install software and you’re ready to start taking calls. Computer software allows for more features to be added. Caller information can be brought up on the computer which will improve customer service. Low costs means it’s affordable for small and large companies.

Diagram of IP PBX

What is a Digital Trunk Line?

The term Trunk Line in telecommunications refers to the high-speed connection between telephone central offices in the Public Switched Telephone Network (PSTN).

trunk is a single transmission channel between two points, each point being either the switching center or the node.

Trunk Group
A set of trunks that are traffic engineered as a unit in order to establish connections between switching systems in which all of the communications paths are interchangeable.

A central office switch connection that has been programmed to treat the circuit as connecting to another switching entity (for example, another carrier’s network). Trunk-side connections offer transmission and signaling features that are appropriate for connecting switching entities.