ISM bands, ISM stands for Industrial, Scientific, and Medical, are license-free frequency bands for industrial, scientific, and medical applications. In these frequency bands, which differ somewhat worldwide, only the transmission power and interference for neighboring frequency ranges are regulated.
SRD (Short Range Device) technology is a radio technology for short distances. It is used, for example, in remote controls for televisions or audio systems, in central locking systems for vehicles, monitoring modules for automotive components, in telemetry for wireless sensors, in telecontrol technology and in alarm systems.
Various "classic" time signal transmitters are in service worldwide, each transmitting the specified time signal protocol on different carrier frequencies and thus providing the basis for a wide range of "atomic clock accurate" synchronized time controls and radio clocks.