ISO/IEC 24730 defines air interface protocols and an application programming interface (API) for real-time locating systems (RTLS). ISO/IEC 24730-5:2010 defines an air interface protocol which utilizes chirp spread spectrum (CSS) at frequencies from 2,4 GHz to 2,483 GHz. This protocol supports bidirectional communication and two-way ranging between the readers and tags of an RTLS. The mandatory default mode ensures interoperability between tags and infrastructure from various manufacturers, while the availability of several options offers flexibility to the developer of the infrastructure to adapt the behaviour of the overall system to the specific needs of his application.