Introduction To Line Telecommunications

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2. History
  2.1 - The Invention of the Telephone
  2.2 - The Developement of Telecoms Network
  2.3 - The Rise of Private Telephone Systems
2.4 - The Dawn of Alternative Networks
2.5 - Milestones in Telecommunications

2.3 The Rise Of Private Telephone Systems

From very early in the development of telephony equipment there have been users who have wanted or required their own private systems. These were called Private Branch Exchanges (PBXs) and Private Automatic Branch Exchanges (PABXs) depending upon weither they were manual or automatic. Since all are now automatic PABX is the correct term. However, today, PBX and PABX may be used interchangeably with little or no confusion.

Modern systems are also called Call Routing Apparatus (CRAs) and it is common for smaller systems to be referred to as CRAs and larger installations as PBXs. This is a peception issue by the general public and does not denote any particular functionality. Indeed the smaller systems are often more feature rich than the larger ones.

Originally PBXs would be the same equipment used by the network provider as the exchange equipment, but located with and under the control of the subscriber. With deregulation and the growth in demand there are now a wide range of systems of all sizes from many manufacturers which are marketed for this purpose.

From the demand for private exchanges there arose the need for closed links to other offices and large customers with high point to point traffic began leasing private circuits to link their systems into private networks.

Private links are rented from the network operator who installs and maintains them. Originally based on analogue technology and signalling systems they were only economic for large users.

Digital technology allowed data and speech to be transmitted across these links via multiplexer equipment together with a reduction in costs which allowed smaller customers access to their benefits. For the lower volume users or less busy networks ISDN can be used to provide a dial up option which connects via the public ISDN system when required and is idle when not needed. Calls will be charged as normal, but this can still be cheaper than leasing a line and not maximising its use.

In recent times these private networks have been changing from fixed point to point to switched systems still point to point but not requiring an single route with connections made as required. These dynamically routing links are called Virtual Private Networks (VPNs) since they appear to the user to be a static link but are in reality continually changing the route used to connect the ends.

2.4 The Dawn Of Alternative Networks

The UK network was created under the control of the General Post Office. This was later split from the post office and British Telecommunications PLC was formed. BT had a monopoly over the provision of services and equipment until the industry was deregulated in 1984.

Deregulation allowed manufacturers and service providers access to the market with a range of goods and services and customers a greater choice of equipment and features.

The result was a massive increase in equipment available and the development of alternative networks whose operators could become licensed as network providers. Although these are separate networks they are all interlinked so that call traffic can be passed between them.



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Introduction To Line Telecommunications
Copyright Panasonic Business Systems UK Ltd 2000