HF-Sendermodul FM TX35/B MC 22 Graupner 4809.35.B The transmitters mentioned at the right can be used in different frequency bands when the HF-module is changed. The channels in the frequency bands are determined by crystals of the corres- ponding frequency band. The transmitter crystal is connected in the HF-modules socket. Frequency band and channel number have to correspond to the receiver system.