VirtualPBX.Com tech tutorials explain certain technical details of general interest to anyone using our VirtualPBX™, cell phones, computers, or other electronic equipment.

A Private Branch Exchange (PBX) or a Private Automatic Branch Exchange (PABX - which is out of fashion since all modern day PBXs are automatic), is a phone switch serving a business or organization and is usually located on the organization's premises. The PBX provides phone services including internal calling, and access to the public switched telephone network. It allows a small number of outside lines to be shared among all of the people of the organization. Advanced PBX phone switches sometimes provide auto-attendant, voice-mail, and ACD (automatic call distribution) services for the organization.

When customers call the company, they typically hear a welcome greeting and instructions to dial the extension of the desired employee, or if the extension is not known to use the company directory by spelling the employee's name.

The PBX provides the physical connection between the outside line used by the caller, and the employee's phone on their desk. It is private because it is owned by the business or organization and is located on their premises, typically in a wiring or phone closet. It is a branch exchange because it makes connections inside of the business in the same way that a normal telephone exchange connects all of the phone numbers served by the phone company.

An old fashioned but concrete example of a PBX is familiar to anyone who has ever seen an old movie showing a business from the 1950's or the film: "Thirteen Days" about the Cuban missile crisis which shows the White-House switchboard in the 1960's. An operator sits at a console with a board in front full of holes for phone jacks with each hole connected to a phone line. When a call comes in, a light at the corresponding jack hole illuminates, and the operator pulls out one of the jack cords, plugs it into the hole with the light, and answers the call with the company name. When the caller tells the operator who they want, the operator pulls out another jack cord and connects the caller to the desired extension. Today, all of these operations are done automatically, either by dedicated PBX circuitry, or by computers controlling the PBX.

A system which can perform the above functions is called a business phone system and is recognizable to anyone that works in an office with an extension on their desk.

Most business phone systems don't directly support auto-attendants and voice-mail, but instead integrate an additional computer that provides the auto-attendant and voice-mail with the PBX. These computers are typically referred to by the acronym, CTI, meaning computer-telephony integration and are an added expense to a company purchasing a PBX. In addition to the PBX, and the CTI computer providing the auto-attendant and voice-mail, a company wishing to install a PBX must typically purchase proprietary phone extensions from the PBX vendor in order to get a functioning phone system.

The VirtualPBX™ provides all of the functionality of a PBX and integrated CTI computer with a twist. The extensions of the VirtualPBX™ are not physically connected to the PBX as in a typical business phone system. Instead, the VirtualPBX™ uses advanced database technology to store routing information, and uses the public switched telephone network to connect the caller to an extension in the company. The extensions can be any telephone that can receive a call, located anywhere in the world.

The VirtualPBX™ requires no equipment to be purchased or installed by the company on their site in order to use it. Thus it is a virtual PBX.