9 MICROWAVE COMPONENTS-NAMELY, RADIO FREQUENCY GENERATORS, RECEIVERS, FILTERS, ANTENNAS AND MIXERS; MICROWAVE DISTANCE MEASURING SYSTEMS-NAMELY, A MICROWAVE GENERATING SOURCE, RECEIVER AND ELECTRONIC PROCESSING CIRCUITS TO MEASURE TRANSMISSION TIME OF A SIGNAL FROM THE MICROWAVE SOURCE TO THE RECEIVER AND CONVERTING THE TIME IN A DISTANCE MEASUREMENT AND MICROWAVE SENSORS FOR ACTIVATING DOOR OPENING MECHANISMS