Abstract: The mobile machine travels underground in a mine along a predetermined path and has a stationary prime mover for driving it. A portable remote control unit is carried by the human operator outside the passenger compartment of the mobile machine, for controlling operation of the prime mover. The portable remote control unit includes a transmitting antenna. When the operator rides in the passenger compartment, he places the portable unit in a special holder therefor. A coupling circuit couples the transmitting antenna of the portable unit, when the latter is inside the passenger compartment with the operator, to an exterior transmitting antenna, so that the substantially closed passenger compartment walls will not prevent transmission of remote control signals. The signals are picked up by a receiving antenna and transmitted to a stationary control unit which correspondingly controls the operation of the prime mover.