Telephone System Design

As with the lighting and power systems within a dwelling the telephone system has changed dramatically since the late 1940s. Then the telephone system was semi-automatic, making an overseas call was a true adventure in fact making a long distance call was an adventure. Now we expect to make a call from any point in the world to any other point in the world whether the telephones are fixed land lines or mobiles or one fixed and one mobile by just dialling a number. Domestic telephones were very rare sixty years ago, it was considered a luxury item. Now it is considered an essential not least because to have an internet connection a telephone line is usually required. Up until the late 1970s the General Post Office (GPO) had a virtual monopoly on telephone services within England they dictated the delivery period for the telephone which was anything up to a year and in some circumstances even longer, they even had to give approval for the message given out by your answerphone if you had one; it goes without saying that the GPO was set up by the Labour Party when in goverment. With privatisation a more commercial approach was made by the GPO's successor British Telecom (BT), now when you need a new line the delivery period is measured in days, and your answer phone message is yours alone to decide, BT was set up by the Conservative Party when they were in government in the 1970s. The GPO had the monopoly over the telephone system, they installed the telephone line, the junction box within the dwelling, the internal cabling within the dwelling and the telephone. Now BT only installs the telephone line and the master socket within the dwelling, they can carry out the rest of the installation of the telephone service although it is more common for 'others' to install the internal equipment and cabling, the monopoly held by the GPO has gone.

As with the lighting and power installation it is the client's brief that will be used to determine the telephone installation.

Telephone cabling is not disimilar to computer network cabling, the plugs and sockets used by the telephone system are known as BT type plugs and sockets or more properly plugs and sockets to BS6312 those by computer networks RJ45 however adaptors between the types are readily available. Therefore the wiring of the telephone system is included in the description of the computer network system.

So this section looks only at the location of the telephone points, the locations of the telephone points should be shown on the client's relevant drawings, if not then an allowance should be made for telephone points in each room apart from bathrooms, external points should also be considered. It must be noted that the provision of a telephone point does not automatically infer that the point will be equipped with a telephone. Consideration should be given to the wireless telephone systems that are available however any device that utilises a radio wave is subject to eavesdropping. Fixed lines can also be listened to however that theoretically requires a proper legal authorisation listening to radio conversations also requires legal authorisation however there are really sad people with scanners that can and do listen in to conversations, satellites operated by foreign countries are not subject to, nor do they conform to, local statutes and regulations; it must be remembered that a government that owns and operates an eavesdropping satellite will have the ability to decode the encryption of digital conversations. There is one other consideration that must be taken into account the IP-PBX which combines PSTN and internet telephony. The location of any IP-PBX must be given consideration, since the telephone cabling should utilise computer network cabling it follows that the two systems will be interchangeable so it is logical to co-locate any telephone system equipment with the computer network equipment.