PBX (Private Branch Exchange)

Having a single or limited wired landline phones at home or small office is easy to handle. But suppose a situation where you own a company having 1000 employees and every employee needs a personal phone on his/her desk. How complicated it would be to have separate phone line to each individual??? Here the role of PBXs starts from.

PBX stands for Private Branch eXchange, it is a private configured network to use telephony within a company or organization. The users can communicate within their company or organization and the outside world, using different communication channels like VoIP, ISDN or Analog.

How PBX works?

Before understanding the working of PBX, lets go back to the early years of telephone lines. At that time telephone operators used to manually redirect the calls to the correct receivers. Businesses used to have different phone lines for different departments, and even in same departments they used to have multiple phone lines for different sections. To connect internally in the office campus too, they had to pay for calls, because each line was a different line with different telephone number. It was so costly and required high maintenance. Then the need of Private Exchanges was realized.

In the 1960s, first PBX system was developed with the help of blocks of switchboards and comparatively less phone lines. The various departments and sections of company were internally connected with the help of switchboards, after which internal calls were possible now. However the number of phone lines and cost of calling reduced but the companies still needed the human telephone operators (to operate switchboards) to transfer calls internally and externally to the right receiver.

Later on as Computers developed, human telephone operators not needed anymore, and PBX systems became little more affordable and popular. Latest PBXs uses an internal numbering system specific to particular company or organization. All the telephones are internally connected to the PBX and assigned with three or four digit number to make call within the network. These are what we referred to as ‘Extensions.’

PBX (Private Branch Exchange)
Work flow of simple on-premise PBX VoIP server setup.

For example in a company of 50 employees the extensions can be allotted as 101,102,103,104… up to 150. Now if employee using extension 103 wants to call employee using extension 109, then he just need to dial 109 from his phone and the call will get connected. For external calls he must dial full outside phone number. Now there is one more thing, business are allotted with overarching business numbers. If any outsider wants to connect with company’s extension, he need to dial the extension number after the business number. Just take the above example, lets assume the business number allotted to this company is 4290, then an outsider should need to dial 4290-109 to connect with employee using 109 extension.

Main Features of PBX

  • It allows internal calls in between the extensions.
  • It can be used to record calls on every extension.
  • We can set separate voice messages for different extensions.
  • Custom Caller tunes can be set.
  • Automatic call distribution (ACD) feature.
  • Automated call answering.

IP PBX – The New Evolution

PBX systems solved many problems of business owners but there were still some limitations using PBX. With the increased use of Internet, many new technologies were developed time after time. Before the internet, all phone calls required analog phones on each end. Then, developers created the ability to transfer and receive voice signals through the Internet data network. This was known as Voice over Internet Protocol (VoIP).

Utilizing VoIP services, new IP based PBX systems were developed known generally as IP PBX, which uses IP phones at the end points. IP phones can be hardware-based or software-based.

Software IP PBX systems are recently very popular among the companies. Using these software anybody can develop their own IP PBX server for personal or professional use. And good news is…some of them are absolutely free to use.