A cathode for a metal air battery includes a cathode structure having pores. A position-detecting unit serves for detecting the piece goods conveyed on the feed conveyer. When a low-rate condition is met, the remote unit enters a low-rate-channel-maintenance mode in which it transmits channel maintenance signaling at either a lower rate or a lower transmit power than when in the high-rate-channel-maintenance mode. An amplitude detector detects the maximum value and the minimum value of the amplitude of the multilevel signal. The disclosed directional control valve includes an accumulator connection for guiding at least a part of the hydraulic oil flowing out from a work chamber into a volume accumulator before the discharge into the tank connection.