室内、隧道及电缆沟等场所，不能承受机械外力。单芯电缆不允许敷设在磁性管道中。
For laying indoors,in tunnels or cable trench,unable to bear external mechanical forces.Singlecore cable in magnetic duct is not permissible.
室内、隧道、电缆沟内或埋地敷设等，能承受一定的机械外力，但不能承受大的拉力。
For laying indoors,in tunnel, cable trench,or direct in ground,able to bear external mechanical forces.but unable to bear large pulling force.
