A system for sending surveillance signals from a hostile environment to an operator. The system comprises an operably movable tractor for ground hauling a trailer and an independently operable drone. The trailer has an actuatable elevator for holding a stockpile of relay sensors and comprising a pair of co-acting elevator belts defining a chute therebetween. The elevator holds a stack of relay sensors for elevation to a pickup-position by the drone. Optionally a conveyor chute may replenish the stack of relay sensors in the elevator.