The aim of this project is to investigate the potential of Rapid Single Flux Quantum (RSFQ) elements for high frequency electronics and the properties of the devices. Using flux quantization in Superconducting QUantum Interference Devices (SQUIDs) the magnetic flux quanta can be used as the units of digital information. Combining SQUIDs in an appropriate manner one can built digital logical circuits. The goal is to investigate the properties of some logical circuits made of high-Tc superconductors.