SRD radio sensors
SRD - short range devices, also known as short-range radio, are freely available frequency bands for everyone. This means that they are not subject to a complex certification process and can be used by anyone, provided that they do not exceed a certain transmission power. In addition, they are particularly robust against interference and are therefore particularly suitable for outdoor sensors and represent an alternative to Bluetooth and WLAN.
Everything started with me with a radio weather station of ELV which in the (868-870 MHz) radio. Later, there was also an ELV FS20 SU-3 flush-mounted wireless switch that controls a floor heating circuit.
They are cheap, can be easily positioned anywhere and are great for quickly realizing or trying things out. Since I use wireless sensors primarily to test things, most of them, after successful testing, are replaced by wired systems. The only sensor that still exists is the wireless weather station.
The receiver is a CUL USB stick is used which is able to read out the 868MHz band. It is therefore also suitable for controlling a large number of other devices. Prerequisite is that they send in the said frequency band. Examples are FS20, FHT, S300, HMS or Homematic.