A multi-core cable includes a plurality of electric wires, a jacket for covering the peripheries of the electric wires, and a strain relief to be mounted on the end of the jacket. The multi-core cable further includes a covering member to be fixed to the peripheries of the electric wires exposed from the jacket. The covering member is contacted with the strain relief to restrict the longitudinal-direction movement of the cable. Due to such characteristics of the multi-core cable, even when the cable is pulled, the connector attached to the cable tip end can be prevented against removal or breakage, thereby preventing the jacket against damage.

An insulator of the cap/pin type for an aerial electrical line comprises a dielectric element that has an outer surface in the form of a skirt that is extended by a metal cap on one side and a metal pin on the other side. It also comprises a mechanical load detection device comprising at least one strain gauge fastened to the metal cap of the insulator so as to be used to detect mechanical stresses representative of a mechanical load exerted on the electrical line.

An insulator of the cap/pin type for an aerial electrical line comprises a dielectric element that has an outer surface in the form of a skirt that is extended by a metal cap on one side and a metal pin on the other side. It also comprises a mechanical load detection device comprising at least one strain gauge fastened to the metal cap of the insulator so as to be used to detect mechanical stresses representative of a mechanical load exerted on the electrical line.