Abstract: A brake operating mechanism engages on an overrun brake present on a trailer, such as a caravan. The brake mechanism includes an actuator operated by pressurized air supplied by a buffer store via a valve controlled by a control unit. Downstream of the brake valve is a valve which is open in the non-operative state and closed during operation. A throttle opening is also provided, the drain capacity of which is greater than the pump capacity of an air pump located upstream of the brake valve and connected to the buffer store. As a result, the actuator moves back under all circumstances, i.e., braking action does not take place, and overheating is effectively prevented.