A method for start-up and/or operation of a communication system composed of at least one multivariable sensor, at least one converter unit and at least one receiving unit, which are connected with one another via a two-wire line. A wherein a primary measured value in the form of an analog signal and extra measured values in the form of an encoded digital signal modulated on the analog signal are provided from the multivariable sensor via the two-wire line, wherein only analog signals are received by the receiving unit. The extra measured values are scaled in the multivariable sensor into formatted values by means of a conversion algorithm, wherein at least the formatted values are requested and received by the converter unit, and wherein corresponding analog signals of the extra measured values are produced from the formatted values in the converter unit by a fixedly predetermined, unconfigurable, reconversion algorithm. The analog signals of the extra measured values are transmitted via respective separate electrical current lines to the receiving unit.