A circuit arrangement for evaluating a received control signal of the type including a first signal of a first predetermined frequency and of a time duration which represents information, and a second signal which immediately follows the first signal in time and has a second predetermined frequency different than the first frequency. In the circuit arrangement the time duration of the first signal is determined by feeding the oscillations of the first signal to a memory which stores a count representative of the number of received oscillations of the first signal, and serially discharging the contents of the memory upon receipt of the second signal and supplying the contents in series to an output terminal which is connected to the control circuit for evaluating and responding to the information.