What’s the Meaning of PBX?

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PBX stands for Private Branch eXchange, and has become a general term used to describe a business telephone system that offers multiple inbound and outbound lines, call routing, voicemail, and call management features. While many IT professionals are well-versed in networking technology, today, they must often also handle (or manage vendors who manage) the company PBX system. The following is a basic primer to give you a better understand of PBX systems.

What Is A PBX?

A PBX is a Private Branch eXchange, a hardware system that handles routing and switching of calls between a business location and the telephone network. Their name originates from the way they interact with the PSTN (public switched telephone network).

"Private" refers to the fact that they are separate from the PSTN, even though they can connect to it. "Branch" describes how a PBX fits into a PSTN: the main communication circuits are called trunk lines, and end points that connect to it and handle smaller amounts of traffic are called branches. "Exchange" refers to the fact that connections are exchanged through a switching system, allowing larger numbers of calls to be routed through a limited number of lines.

What Does A PBX Do?

It handles the same functions as old-fashioned telephone operators, who once sat at large manual circuit boards, spoke with each caller to learn who they were trying to reach, and manually plugged wires into connectors to complete calls. Modern systems are automated, incredibly speedy, and can do a great deal more than any manual operator.

A PBX also provides sophisticated calling features such as call waiting, auto-attendants, music/message on hold functions, and voice mail. Advanced features like find-me-follow-me, very useful for companies with highly mobile employees or sales forces, are also provided through a PBX.

What Are Key Systems? Are They The Same As A PBX?

No, the two are actually quite different. A key system is typically only useful for small businesses, with limited numbers of users (typically less than 50). A key system has telephones with multiple buttons ("keys") with lights that indicate which lines are in use , like you might expect to see on a receptionist’s desk. It is limited in function and feature set. Unlike users on a PBX, users on a key system typically do not have an assigned extension or Direct Inward Dial Number (DID) that rings only their phone. In fact, a common key system configuration is to setup incoming calls to "Ring All" (i.e. all incoming calls ring on all phones). It is also less common for key system users to have a private voicemail box.

What Are The Types Of PBX?

There are four main types of PBX systems, distinguished by location and operation. A PBX may be located on the premises of the business, or offsite at a PBX management office. They may operate by Internet protocol (IP) or by older technologies like analog or digital phone lines.

The Four Types Are:

Traditional PBX

  • On-premise PBX (located at the business, using analog or digital systems)
  • Hosted Traditional PBX (located offsite, using analog or digital systems)

IP-Based PBX

  • On-Premise IP PBX (located at the business, using IP communications)
  • Hosted IP PBX (located offsite, using IP communications)

How Does A PBX Work?

A PBX is based around a PBX board. Years ago, that meant an exposed wiring panel with sockets into which an operator plugged wires to complete the connections for calls. They were, literally, boards with sockets connected to dense packs of wires through which calls were routed. Today they are circuit boards: very compact and very efficient.

The heart of a PBX is a specialized computer that evaluates the routing needs of large numbers of communication paths, correctly routes many links simultaneously, and makes efficient use of limited amounts of bandwidth. What once required human operators and a gigantic workspace now fits into a single slot in a server rack.

Hosted PBX comes in two main varieties: the standard hosted system, and virtual PBX. Standard hosted systems are like an onsite PBX but physically located at service a provider’s server center. Virtual PBX is a term often used interchangeably with Hosted PBX, but in some cases there is a distinct difference: virtual PBX may refer to a very simplified system that handles only call routing in single locations. Such systems may struggle with multi-site applications, direct inward dial, or many of the more robust features included in an actual hosted PBX.

Why Choose One Type Over Another?

Each business telephone system configuration has advantages and drawbacks. When choosing the configuration for a business, the easiest way to determine the right option is to examine two main variables: location and communication type.

Onsite Vs. Offsite

Onsite systems (on-premise PBX) offer more direct control over the phone system’s operation. When a business needs to add, change, or delete a line from the system, it can be handled in-house. This requires a high level of expertise from onsite IT professionals, however. Offsite, or Hosted, options shift the responsibility for configuration and maintenance to a service provider. Direct control of the system is limited, but a company’s IT staff needs only a basic understanding of the phone system.

Analog/Digital Vs. Internet Protocol

Analog systems use traditional wiring and are generally distinct from a company’s computer networking hardware. IP-based systems are integrated into the same networking systems used for sending and receiving e-mail, web browsing, and other online functions. Traditionally-wired systems sometimes had fewer call-quality concerns than early IP-based systems – though modern ones on strong networks have greatly improved. Using IP-based systems often allows a company to have all its communication needs handled by one provider, simplifying billing and support concerns.