Telecommunication Circuits in Building

The design of telecommunication systems is beyond the scope of this post, but the provision that has to be made for them within a building in described here.

In many cases all that is needed is a route by which the telephone service can bring in a telephone cable to an instrument. Telephone cables are quite small and if the position of the outlet for the telephone receiver is known it is sufficient to install a 20 mm conduit from out side the building to the outlet with the same number and spacing of draw-in points as are used for any other conduit system.

Some buildings may have an internal telephone system which may consist of extensions to the public telephone or may be an entirely separate installation. Here again the essential matter for the electrical services designer is to agree on the outlet positions with his customer and to arrange for them to be linked to each other by conduit or trunking.

Trunking can be useful alternative to conduit when the system is a complex one needing many cables with a large number of junctions. Telephone cables do not have a protective sheathing and therefore need the mechanical protection of conduit or trunking. Where practicable, a separation of at least 1.8 m shall be maintained between conductors of communication systems on buildings and the lighting conductors.