Aspects of a method and system for transmitting multiple channels on FM bands may include generating from one or more baseband signals, a plurality of radio frequency transmission signals each at a different radio frequency, wherein the one or more baseband signals comprise an in-phase signal component andor a quadrature signal component. According to the method of the invention an important part of the radiation hits the walls of the furnace and are reflected there before it is transferred to the blank. A repetition period coding unit compares the evaluation values provided for the predetermined number of candidates with one another, selects one candidate from the predetermined number of candidates according to the comparison result, and furnishes selection information indicating the selection result, excitation source location code, and polarity code. Further provided is the monitor unit employing narrow, widely-spaced, fast rise-time, fast transition-time pulses for conductivity measurement and alarm activation.