The invention relates to a control circuit (1) for an apparatus comprising a heating device for preforms, a blow molding machine for producing containers from preheated preforms, a first measuring device (15) for determining an actual temperature of the heated preforms and a second measuring device (9) for determining an actual light transmission of the containers, wherein the control circuit for controlling the light transmission of containers comprises: A higher-level control circuit having a first comparator (4) for determining a first control difference (5) from a target light transmission (2) and an actual light transmission (3) and having a first controller (6) which, based on the first control difference as a first input variable for a system (16), outputs a first adaptation (7) of a process parameter of a station of the blow molding machine as a first output variable and controls the process parameter of the station of the blow molding machine in accordance with the first adaptation. The first controller also outputs a target temperature (8) of the heated preform as a second output variable, based on the first control difference as an input variable. A subordinate control circuit having a second comparator (11) for determining a second control difference (12) from the target temperature and the actual temperature and having a second controller (13) which, based on the second control difference as a second input variable for a system (16), outputs a second adaptation (14) of a heating behavior of the heating device as a third output variable and controls the heating behavior of the furnace in accordance with the second adaptation (14).