Multi-core cable

A multi-core cable, comprising:

• a heat detection line comprising a twisted pair wire comprising a pair of heat detecting wires being twisted together, each heat detecting wire comprising a first conductor and a first insulator covering around the first conductor, a jacket covering around the twisted pair wire, and a binder tape collectively covers around the twisted pair wire, and the jacket covers around the binder tape;
• a plurality of electric wires spirally twisted around the heat detection line, each electric wire comprising a second conductor and a second insulator covering around the second conductor;
• and
• a sheath covering the heat detection line and the plurality of electric wires together,
• wherein the jacket comprises an inner layer, an outer layer, and an intermediate layer provided between the inner layer and the outer layer, and
• wherein a hardness of the outer layer is higher than a hardness of the inner layer.