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A Brief History Of Pbx

Business telephone systems have been a long time in their development to where they are today, developing from simple key systems requiring multiple phone lines to virtual PBX (private branch exchange) existing in cyberspace and functioning in conjunction with a company’s existing data transfer.

Some of the first popular phone systems were the “1A2 Key System”. These varied considerably and had a firm grasp on the market for many years around the 1950’s. The KSU (Key Service Unit) acted as a central control unit and calls were redirected from there via a physical mechanism contained in the phone. This permitted features such as intercom services and hold features with music. These simple features could be achieved on a line by line basis by hardwiring a backplane into the central control unit. A lamp feature for each line allowed users to quickly determine the status of all phone lines accessed by their phone.

PBX was first used to describe such “key systems” where switchboards were run by hand. PBX gradually started to use automated systems instead of operators. As this became more common, the terms PABX (private automatic branch exchange) and PMBX (private manual branch exchange) came about to differentiate between the two systems. EPABX (electronic private automatic branch exchange) was also used to describe various digital systems.

One of the main reasons for such systems was to reduce the cost of internal calls, since calls could be made over the private branch and not incur local call costs. As the systems developed, other features such as extension dialling, call forwarding and various forms of line hunting became available.

The next major development was with the rise of data networks and the internet. Since many companies already had packet switch networks due to the need for data transfer, it became viable to use a phone line over their existing data connection and hence VoIP (Voice over Internet protocol) came about. Far from perfect, VoIP to this day can still have issues with latency and power cuts which can render it inoperable.

VoIP’s main advantage, however, was its cost. This is due to the way data is charged compared to standard phone connections. Typically, a phone connection is charged on a connection time basis, so there is a charge regardless of data transfer. Packet switching connections, however, tend to charge based on the number of packets (or amount of data) being transferred, which, even under high load, tends to result in much lower costs.

Since many systems were now operating via data connections, it was recognised that many companies didn’t have requirements for large in-house PBX systems, and as such, hosted PBX came about. A hosted PBX system is a service whereby the phone system is a service and requires no capital investment in the hardware needed to run it. This is particularly advantageous for smaller companies in several ways; often such systems are very easily scalable. With hosted systems, companies can simply increase or decrease their contract instead of buying a system which is larger than their needs and paying a large amount of capital or later having to expand their system in house.

Thus PBX is a term with a myriad of meanings. Having started as manually operated switchboards and going through several phases of development to modern day telephone systems, the term is now used to describe many complex telephone systems, where often there is in fact no private branch, and no exchange.

By: Don Rev

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The author works for a company who are experts at implementing Telephone systems and business telephone systems with Business phone system UK and Telephone systems UK

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