Abstract: The coolant supply to a cooler for the detector of an optical seeker in a missile is to be controlled; the missile is arranged in a launcher attached to an aircraft. A caging device for caging the movable seeker optical system of the seeker is provided in the seeker. For target tracking, this caging device is releasable, before operation of the missile, by a release signal through a control line extending from the cockpit of the aircraft to the launcher. This control line is simultaneously used for controlling the coolant supply by providing a bistable circuit on the missile side of the control line, activation of the coolant supply being effected by setting the bistable circuit, the setting and resetting of the bistable circuit being determined by the variation in time of the release signal.