  Single flux quantum (SFQ) based circuits are the subject of renewed attention
due to their high speed and their very high energy efficiency. However, the
need of cryogenic temperature, the complex physics of Josephson junctions and
the lack of proper EDA tools causes slow progress in the field of
superconducting electronics. In this work we introduce a new open source
program named JOsephson INterface Utility Software (JOINUS [1]) that
incorporates SPICE-based simulator engines, improved physical models and
several powerful built-in routines. JOINUS is based on a user-friendly
environment available on Linux, MacOS and Windows platforms to simplify the
design and analysis of superconducting digital circuits.
