The IF signal is internally fed via a 3-stage controlled wideband amplifier to the video demodulator and the phase detector. The phase detector compares the phase of IF signal (0) with the output signal of the VCO (90) and sets the VCO frequency accordingly. A lock detector switches the PLL loop filter according to the state of the PLL (locked-PLL slow, unlocked-PLL fast). A second output of the VCO (0) provides the reference carrier for the video demodulator. The polarity of the demodulator can be inverted by the standard switch (Pin 11), so that negative or positive modulated IF signals