Ans : Single steel tape armouring:Single steel tape armouring is used principally for parkway cables, cables suspended on a messenger or clamped at intervals in shaft and tunnel installation or cables buried directly underground where a mechanical outer protection is required but longitudinal are not involved.
Double steel tape armouring: Double steel tape armouring is used particularly for low tension cables installed indoors or aerially outdoors or directly buried underground where a good protection against crushing or penetration by sharp bodies is required and not likely to be subjected to tensile stresses.
Single wire armouring: Single wire armouring is used in cables where the armouring is subjected to have longitudinal strength such as for cables pulled into duct, used for river crossing, laid in marshy ground or in colliery districts where soil subsidence may occur, vertical cable runs and for cables hung on brackets along side railways or tunnels etc.
Double wire armouring: Double wire armouring is used chiefty for vertical run of large size cables as in a mine shaft, submarine or dredger where easy handling and greater flexibility for the same conductivity with high longitudinal strength is required.