What does private branch exchange mean?

A private branch exchange (PBX) or private branch exchange (PBX) is a corporate telephone system whose job it is to redirect (redirect) incoming calls to users on local lines and to allow anyone to share a specific number on external telephone lines (those used by operators, long distance calls called).

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In contrast to the public telephone network (PSTN), this system saves the costs of one telephone line per user to the operator’s headquarters.

The PBX, which is a professional or personal telephone system, is owned by the company that operates it and not by the telephone company, which may continue to provide equipment or managed services. PBX systems were originally analog. Nowadays most use digital technologies: digital signals are converted to analog signals for outgoing calls that use the subscriber line of a traditional telephone service.

Note that the digital telephone system can still integrate network switching systems that support internal analog telephones.

How does a PBX work?

The hardware elements of a PBX depend on its complexity: conventional PBX with copper wire circuitry, combination of analog and digital lines, use of VoIP (Voice over IP) telephony, which is hosted by the company, or a cloud-based system . Each system is described below.

In conventional PBX telephone systems, landline telephone lines are connected to a PBX box on the company premises. This box contains switches that distribute calls between the company’s telephones and provide access to external, so-called trunk lines.

An IP-PBX or IP-PBX (Internet Protocol PBX) or even IPBX uses digital signals instead of analog lines to process calls. In this case, traditional telephone cables are replaced by Ethernet cables. IP PBX systems can also be hosted with service providers. This solution is billed monthly, but results in lower material costs.

There are backup PBX systems, often referred to as Virtual PBXs (VPBX), which are generally marketed as a hosted service with less functionality. These are best for small businesses.

Features of PBXs

The hardware elements of a PBX depend on its complexity and use (e.g. the types of telephones in a particular location). In general we find:

multiple telephone lines that terminate at the PBX; a computer that manages the switching of calls within the PBX for both incoming and outgoing calls; a network of internal telephone lines to the PBX; a Unified Communications router (wireless and wired); Telephone receiver (USB, VoIP and SIP); a VoIP gateway; an IP PBX; an internet router; Cables, cabinets, an uninterruptible power supply system (inverter); a telephony application server.

A PBX call center manages incoming and outgoing calls and integrates automatic management solutions for incoming calls. Among them are: the interactive voice response (IVR); Call screening, generally used to assess employee productivity and training needs; Conference call functions; Features that enable employees to take and make calls from their workstations; Integration with customer relationship management (CRM) systems to facilitate the collection of logistical information and the transmission of customer information to agents; Predictive dialing systems.

In some cases, a PBX can be replaced with a Centrex (CENTral Office EXchange) service that consolidates operator-leased lines, push-button telephone systems for routing calls and for small businesses. through a digital network with integrated services for primary rates (ISDN-IDP).

Many providers market corporate PBX systems: for example Nortel, Rolm / Siemens, NEC, Fujitsu, Cisco, Avaya and Alcatel-Lucent.

Differences between a PBX and a private branch exchange

A private automatic branch exchange is a type of automated telephone system. The term PABX was originally used to distinguish modern automatic systems from old manual systems (PMBX, Private Manual Branch Exchange). Since all modern PBX systems are now automated, this distinction no longer applies and the two acronyms PABX and PBX are interchangeable.

PBX and VoIP

The traditional PBX system uses historical telephone lines, while the VoIP system sends and receives phone calls over the Internet. Despite the dependence on the broadband network, VoIP telephony is now widespread. Current offers such as the IP telephone system offer almost unlimited possibilities for a growth in the number of sets and lines.

In addition, they integrate advanced features (call groups, queues, digital receptionists, voicemail, call reporting) that are more expensive and complex with a traditional telephone system.

The tariffs and the size of the PBX provider are decisive factors when choosing your telephony solution.
Large companies that spread their investments among several dozen users are best placed to give free rein to their desires for new technologies and specific functions.
Smaller businesses, which are generally more cost-conscious, can make significant savings by using digital phones attached to existing phone lines. However, you should be aware that the costs can increase if new cables have to be pulled or if the local area network (LAN) does not support Voice over IP.

Small offices and businesses do not need primary PRI (Primary Rate Interface) access as a few phones (up to 15) on traditional copper lines may be sufficient for their needs. For all these facilities, the choice of new telephone system can be made between an Internet VoIP service (telephony hosted by VoIP companies) and a modestly sized modern digital system, knowing that the initial investment per station to install a IP PBX doing business can be very high.

Costs of a PBX

The question of cost is crucial in choosing a telephony option, especially as free or almost free services like Skype are becoming increasingly popular with businesses. In addition, management policies aimed at lowering operating costs in the short and long term encourage the migration to VoIP.

Companies save money quickly with Internet telephony, as the monthly rates are lower than with TDM systems (Time Division Multiplexing) and the normally free extended functions are integrated into standard systems.

In addition, VoIP domestic long distance calls are inexpensive and international calls are less expensive. These savings must of course be seen in the context of the overall cost of migrating to VoIP. However, the savings brought about by network convergence are significant as the data traffic is carried from the dedicated voice network to the data network.

Migrating to VoIP can also lower hardware costs, as the costs for IP telephony systems and handsets are lower than for maintaining old systems.

However, we must be wary of the potential hidden costs associated with upgrading local networks to support VoIP, such as: B. the costs of terminating current contracts with telephone providers. Enterprises moving to VoIP may need to expand their network capacity to handle voice traffic and possibly add SIP trunks. You also need to incorporate new network management capabilities to prioritize voice traffic and keep the VoIP network secure.

Last point: It will likely be necessary to provide network infrastructures for VoIP, e.g. B. Media Gateways and Session Border Controllers (SBCs). In conclusion, the lower cost is a strong argument in favor of VoIP, but only if all other factors are carefully considered.

Use case

In addition to the question of cost, the migration to VoIP systems can be justified by the need to rejuvenate PBX systems. In some companies, old TDM systems no longer meet the requirements and have to be replaced.

While telephone equipment is sufficient for corporate use, employees have switched to cutting-edge technology for their personal use and are gradually turning away from traditional telephony. TDM systems cannot be compared to modern web or mobile communication tools.

In contrast to TDM systems, employees make extensive use of web tools (e-mail, chat and video) that integrate VoIP. VoIP also offers the advantage of integration with data applications in the local network and enables companies to migrate telephony management to the cloud. Another strong argument: IP telephony has a positive impact on productivity, especially thanks to visual voicemail and ad hoc conferencing that employees can use to remotely manage missed calls.