The previous chapter gave a broad overview of the field of wireless connected sensors, operating at the edge of the IoT, with a focus on sensing devices for biomedical applications. This chapter will provide the reader with a system-level insight in a typical biomedical sensor system. In Sects. 2.1 to 2.6, the most important building blocks of a biomedical recording system will be revised, from the electrodes to the transmitter. In Sect. 2.7, a small case study of a wearable will be discussed. In Sect. 2.8 several data processing techniques will be discussed, both in the digital and in the mixed-signal domain.