Need for cable planning
With the increasing size of telephone exchange systems in most cities and towns in India, subscribers connections are being given through underground. Cables to an increasing extent, As the use of underground cable networks becomes progressively more common it becomes necessary to plan the network well ahead of the time demand for telephone connections actually arises.
Purpose of planning
The main idea behind proper economic cable planning is the availability at optimum cost of the cable pair of proper type as and when required for the purpose of maintenance and new connections. The cable component form a substantial portion of the capital cost of local telephone project. Hence proper cable planning will effectively reduce such capital cost without hindrance to maintenance and new connections.
The planning work can therefore be considered in its two broad aspects viz.
(a) Anticipation of telephone demands
(b) Determination of an economical and convenient manner in which cable provision can be made to meet these demands.
Anticipation of telephone demands
Forecasting is done generally for a period of 20 years as it covers the economic planning period of most of the components of a telephone exchange project. A document namely Telephone demand projections – cities and selected towns available in all circle offices will supply the data relating to the anticipated telephone demands in a particular area. The forecast based on the above document will give the figures generally at 6 years interval, called the base data.
Preparation of cable plan and their approval
The cable network in a telecom project should be executed in a co-ordinated manner matching with the installation of exchange equipment. Normally the cable component of the project takes a very long time. Hence the cable network need not be waited for the sanctioning of the project. As soon as the firm allotment of exchange equipment is received, the cable plans. wherever necessary are prepared and got approved by the competent authority well in time.
The cable network is to be so co-ordinated that all the associated cable component works are completed about 3 months in advance of the commissioning of the exchange.
In this type of network two cross connection points viz. cabinets and pillars are provided between exchanges and DPs to maintain the flexibility by using a particular cable pair within a number of DPs.
(a) Primary cable:- The cable laid between exchange and cabinet is called primary cable. The gauge of such cable is normally 0.4 mm. the recent development is the use of 0.32 mm dia. conductor and consequently there will be huge saving of copper.
(b) Secondary cable:- This cable is linking the cabinet with pillar and the
normal gauge of conductor is 0.5mm.
(c) Distribution cable:- DPs are connected to the pillar by these type of cable. The gauge varies from 0.5 mm, 0.63mm depending upon the distance of the DPs from the pillar.