Purpose – This paper explains the basic characteristics of signal transmission in communication systems. Transmission channels such as copper and aluminum conductors, radio transmission and optical transmission are explained. Major aviation protocols are presented in their functioning. The signal processing and transmission are shown on the basis of the fuel level indicator. Decision guidance for the selection of sustainable avionics is provided. --- Methodology – Transmission channels are compared in terms of bandwidth, cost and interference factors. Signal transmission in the application case of the fuel level indicator is carried out by measuring the sensor resistance and the further signal processing with a microcontroller. --- Findings – For the individual application, a suitable selection of microlight communication systems is presented. Currently, the RS-232 standard (point-to-point connection) is still used to connect electrical devices from different manufacturers. For larger series production of microlight aircraft, a BUS set up with CANaerospace is an attractive option. Cloud networked systems are expected to be the future of avionics systems. Wireless communication protocols, such as ZigBee are a sustainable solution due to their modular adaptability to different requirements. --- Practical Implications – Knowledge of signal transmission can help engineers design better systems for microlight aircraft, affecting safety, cost and weight. --- Originality – After research, communication systems and avionics systems for microlight aircraft have not been covered in any scientific work. The listing of aviation protocols to this extent with their functionality has also not been published in open access. Own concepts for future avionics systems, such as a digital compass pointing to true north, are developed (Mag2True). Furthermore, the software for the fuel level indicator was developed from scratch as part of the thesis.