Product Details

With a PBX, you can enjoy benefits such as making internal calls for free and creating a features package that matches your business needs perfectly. Use this section to get a basic overview of the PBX and what it can do for your business.

What is a PBX?
How Do PBXs Benefit Businesses?
How Do PBXs Work?
PBX Functionality Expands

What is a PBX?

A private branch exchange (PBX) is a system/platform that routes voice, data, and video transmissions through equipment located on the customer's premises. PBXs do not require the services of the provider's central office. PBXs may be programmed and customized to meet specific customer needs. They are sold primarily to mid-size and large businesses.

A PBX routes calls:

• Between users within an organization
• From users within an organization to users outside of the organization
• From users outside an organization to users inside the organization

PBXs provide inexpensive communications within an enterprise and effective sharing of external communication trunks for communications with more than one billion other phone sets and mobile phones worldwide.

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How Do PBXs Benefit Businesses?

With a PBX, businesses can choose from a wide variety of features to create the system that best meets their needs. And if your business needs change, you can easily add or delete features by installing the software for the new features. There's no need to reprogram each line separately.

PBXs make it easy for businesses to upgrade to innovative technologies and take advantage of the many applications that are available. PBX systems are compatible with existing technologies such as integrated services digital network (ISDN), Internet Protocol (IP), frame relay, asynchronous transfer mode (ATM), and local area networks (LANs).

If a business wants to make a network change for the entire company, including remote locations, it's easy: all the business has to do is program the change into the PBX one time. There's no need to adjust each individual line or go through a communications provider, as with a Centrex system.

Some of the other benefits include:

• Backup systems that exist in their memory, so there is virtually no chance of an outage.
• Free internal calls, which means substantial savings for businesses with a large number of employees.

A PBX performs three basic functions:

• Establishes end-to-end connectivity among its subscribers (on-net) and from its subscribers to remote subscribers (off-net), through intermediate nodes (other PBXs or central office (CO) switches on the public switched telephone network (PSTN)) in response to a call request.
• Supervises the circuit to detect call requests, answer, signaling, busy, and disconnect.
• Disconnects the path upon call termination to make resources available to other users.

A traditional PBX consists of:

• Lines: These serve as the transmission path from a non-switching subscriber terminal to a switching center.
• Trunks: These external carrier lines connect the PBX system on the customer's premises to the public network. Customer trunks may be outgoing only, incoming only, or two-way. Trunks perform various control functions associated with call processing.
• Processor(s): A processor is a programmable device that controls the operations of a PBX, such as monitoring lines and trunks, establishing paths through the switching matrix, tearing down connections upon call completion, handling voicemail, and recording of billing and traffic information.
• Memory: Memory enables the processor to implement the functions of the PBX.
• Nonvolatile memory (ROM) contains the operating instructions and stores system configuration information.
• Volatile memory (RAM) is used for temporary storage of frequently used programs or for workspace.
• Switching matrix: Controlled by the processor, the switching matrix interconnects lines and trunks either through space division switching or time division switching.

In recent years, the functionality of the traditional PBX has expanded. The PBX of the future is computer-based. It will permit the integration of voice and data over T1 trunks and ISDN, add LAN and Internet connectivity, and support ATM as well as management via simple network management protocol (SNMP).

The future of the PBX will no longer be proprietary. Although today customers usually have to purchase upgrades and enhancements from the initial manufacturers, the PBX of the future will operate in an open system environment, permitting the integration of a wide array of hardware and software from a variety of competing manufacturers. Although the market for such systems is still in its infancy, it will expand exponentially within the next decade.

• Server/PC-based PBX (also called PC/PBX or UnPBX)

The local server or PC is equipped with the cards and software to perform PBX functions, such as call forwarding, call hold, and call transfer. This allows for greater control and programming flexibility.
• IP-PBX

IP capability enables customers to route calls over either the corporate intranet or the Internet. Vendors incorporate this feature into traditional PBXs or server/PC-based PBXs either through an IP card or a gateway/server between the public network and the corporate voice equipment.
• PBX Interface Cards

These cards interface traditional and server/PC-based PBXs with outside networks and desktop stations
• Integrated Communications Platforms (ICPs)

ICPs offer integrated voice and data communication capabilities. They are standards-based communications platforms that can integrate several pieces of voice and data communications equipment, including PBXs, LAN hubs, routers, computer-telephony servers, remote access servers, voicemail, automatic call distribution (ACD) and interactive voice response (IVR), into one box.