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Private Branch Exchange - PBX

 

What is a PBX?
A PBX (Private Branch Exchange) is a switch station for telephone systems. It consists mainly of several branches of telephone systems and it switches connections to and from them, thereby linking phone lines.


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 to make a call to another phone in the network. We often refer to this number as an extension.


This picture shows what a PBX does.

 

The Functions of a PBX
A PBX (Private Branch Exchange) is a switch station for telephone systems. It consists mainly of several branches of telephone systems and it switches connections to and from them, thereby linking phone lines.


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 to make a call to another phone in the network. We often refer to this number as an extension. A person calling from the outside might ask for an extension to be directed to the person she is targeting.

 

The main technical roles of a PBX are:
• To switch between telephone users thereby creating connections
• To make sure the connection remains in place properly by keeping its resources
• To properly end the connection when a user hangs up
• To record the quantities, statistics and metering related to the calls

 

Practically, the functions of a PBX are the following:
• Provide one single number that external callers can use to access all persons in a company.
• Distribute calls to employees in a answering team in an even way; using the Automatic Call Distribution (ACD) feature.
• Automate call answering, but offering a menu of options from which a user can select to be directed to a specific extension or department.
• Allow the use of customized business greetings while answering calls.
• Provide system call management features.
• Place external callers on hold while waiting for a requested person to answer, and playing music or customized commercial messages for the caller waiting.
• Record voice messages for any extension from an external caller.
• Transfer calls between internal extensions.

 

IP-PBX
PBXs are not only for VoIP but have been around for landline telephone systems as well. A PBX that is specifically made for VoIP is called an IP PBX, which stands for Internet Protocol Private Branch Exchange).


Up to now, PBXs have been a business luxury that only huge companies could afford. Now, with IP-PBXs, medium-sized and even some small companies can also benefit from the features and functionalities of a PBX while using VoIP. True they have to invest some money into hardware and software, but the return and benefits are considerable in the long term, both operationally and financially.

The main benefits that an IP-PBX brings around are scalability, manageability and enhanced features.
Adding, moving and removing users to an from a telephone system can be very costly, but with an IP-PBX it is as cost-effective as it is easy. Moreover, an IP phone (which represents terminals in a PBX phone network) may not necessary to attached to one specific user. Users can transparently log in the system through any phone in the network; without however losing their personal profiles and configurations.

IP-PBXs are more software based than their predecessors and so maintenance and upgrade costs are considerably reduced. The work is easier as well.

PBX Software

An IP-PBX needs a software to control its mechanism. The most popular PBX software is Asterisk which is a good open-source software.

 

Private branch exchange (PBX)
A PBX (private branch exchange) is a telephone system within an enterprise that switches calls between enterprise users on local lines while allowing all users to share a certain number of external phone lines. The main purpose of a PBX is to save the cost of requiring a line for each user to the telephone company's central office.

The PBX is owned and operated by the enterprise rather than the telephone company (which may be a supplier or service provider, however). Private branch exchanges used analog technology originally. Today, PBXs use digital technology (digital signals are converted to analog for outside calls on the local loop using plain old telephone service (POTS ).

 

A PBX includes:
• Telephone trunk (multiple phone) lines that terminate at the PBX
• A computer with memory that manages the switching of the calls within the PBX and in and out of it
• The network of lines within the PBX
• A console or switchboard for a human operator (optional)


In some situations, alternatives to a PBX include centrex service (in which a pool of lines are rented at the phone company's central office), key telephone systems, and, for very small enterprises, primary rate Integrated Services Digital Network (ISDN).

 

Private automatic branch exchange (PABX)

A PABX (private automatic branch exchange) is an automatic telephone switching system within a private enterprise. Originally, such systems - called private branch exchanges (PBX) - required the use of a live operator. Since almost all private branch exchanges today are automatic, the abbreviation "PBX" usually implies a "PABX."


Some manufacturers of PABX (PBX) systems distinguish their products from others by creating new kinds of private branch exchanges. Rolm offers a Computerized Branch Exchange (CABX) and Usha Informatics offers an Electronic Private Automatic Branch Exchange (EPABX).

 

IP PBX (private branch exchange)
An IP PBX is a private branch exchange (telephone switching system within an enterprise) that switches calls between VoIP (voice over Internet Protocol or IP) users on local lines while allowing all users to share a certain number of external phone lines. The typical IP PBX can also switch calls between a VoIP user and a traditional telephone user, or between two traditional telephone users in the same way that a conventional PBX does. The abbreviation may appear in various texts as IP-PBX, IP/PBX, or IPPBX.


With a conventional PBX, separate networks are necessary for voice and data communications. One of the main advantages of an IP PBX is the fact that it employs converged data and voice networks. This means that Internet access, as well as VoIP communications and traditional telephone communications, are all possible using a single line to each user. This provides flexibility as an enterprise grows, and can also reduce long-term operation and maintenance costs. Like a traditional PBX, an IP PBX is owned by the enterprise.


What are the different types of private branch exchange (PBX) systems?

A PBX is the standard telephony system used in enterprises and is fairly common among small and medium-sized businesses. A PBX is known as a switched system, providing a centralized infrastructure for telephony. This allows for a consistent environment for all employees with access to the PBX, such as common features and an internal dialing plan with user-assigned extensions. From an IT perspective, the PBX allows for centralized control and management across the system.

 

Prior to the advent of Internet Protocol (IP), there really was just one type of PBX. The other options to a premise-based system would be a key telephone system or a central office exchange service (Centrex). The former is a scaled-down PBX, more suitable for smaller businesses with simpler needs. Centrex has long been a staple of campus environments that need PBX-like capabilities, but at a lower cost in the form of a hosted system that is leased rather than owned.


With IP now becoming the standard for telephony, the PBX has evolved into the IP PBX. Legacy PBX systems still account for most of today's installed base, but the vast majority of new purchases and upgrades are IP PBX. The systems are similar at their cores, but IP-based systems are less capital-intensive and offer more flexibility in terms of adding new features and integrating VoIP with other communication modes.




 

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