CR 300 is a summary designation for a receiver system the basic design of which allows for a large number of special requirements to meet by means of a number of additional plug-in subunits . The control system of the receiver has been designed so as to allow for use in very modern communication systems as for instance radio exchange systems and automatic channel scanning, etc. All subunits can be exchanged without the need of alignment, which makes maintenance simpler and cheeper.The frequency processing plan with a high (139.3 MHz) fixed first intermediate frequency makes it possible to exchange the HF-stages of the receiver to a parametric up-converter with crystal filter for the first intermediate frequency should this technique in the future prove advantages technically and economically. The receiver described below, CR 301, can be completed for reception of I.S.B. by adding two subunits. Only about 15 minutes will be needed for this operation. The local oscillator outlets from the synthesizer are doubled and can together with the control signals of the receiver, be made available on the rear panel of the receiver. In this way two receivers, one without a synthesizer, can be operated in diversity.