Power transmission apparatus with an input (E) for connecting to a drive unit which can be operated at a constant rotational speed, and at least one output (A) for connecting to a mobile machine which can be operated at a variable rotational speed, comprising: - a hydrodynamic rotational speed/torque converter which is configured as a counter-rotating converter with at least one pump impeller (P), a turbine impeller (T) and a diffuser (L) which form a working space which can be filled with operating medium; - a superimposition transmission with at least one planetary gear mechanism , comprising an internal gear , a sun gear and a planetary carrier with a plurality of planets as elements of the planetary gear mechanism , the input (E) of the power transmission apparatus being connected at least indirectly, preferably directly, to the pump impeller (P) of the counter-rotating converter and to a first element of the planetary gear mechanism , the turbine impeller (T) of the counter-rotating converter being connected at least indirectly, preferably directly, to a second element of the planetary gear mechanism , and a third element of the planetary gear mechanism being connected at least indirectly to the output (A) of the power transmission apparatus or forming the said output (A); characterized by the following features: - the counter-rotating converter can be emptied; - with a switchable variable-speed coupling for transmitting the power in a first rotational speed range in the case of an emptied counter-rotating converter between the input (E) and the output (A) of the power transmission apparatus ; - with a device for the at least indirect supporting and/or fixing of the second element of the planetary gear mechanism , in particular the connection between the turbine impeller (T) of the counter-rotating converter and the second element of the planetary gear mechanism in the said first rotational speed range. - a hydrodynamic rotational speed/torque converter which is configured as a counter-rotating converter with at least one pump impeller (P), a turbine impeller (T) and a diffuser (L) which form a working space which can be filled with operating medium; - a superimposition transmission with at least one planetary gear mechanism , comprising an internal gear , a sun gear and a planetary carrier with a plurality of planets as elements of the planetary gear mechanism , the input (E) of the power transmission apparatus being connected at least indirectly, preferably directly, to the pump impeller (P) of the counter-rotating converter and to a first element of the planetary gear mechanism , the turbine impeller (T) of the counter-rotating converter being connected at least indirectly, preferably directly, to a second element of the planetary gear mechanism , and a third element of the planetary gear mechanism being connected at least indirectly to the output (A) of the power transmission apparatus or forming the said output (A); - the counter-rotating converter can be emptied; - with a switchable variable-speed coupling for transmitting the power in a first rotational speed range in the case of an emptied counter-rotating converter between the input (E) and the output (A) of the power transmission apparatus ; - with a device for the at least indirect supporting and/or fixing of the second element of the planetary gear mechanism , in particular the connection between the turbine impeller (T) of the counter-rotating converter and the second element of the planetary gear mechanism in the said first rotational speed range. <EOS>