The standard version of the iss contains a rain collector, temperature sensor, humidity sensor and Anemometer. In addition to the standard weather features, the iss Plus adds a pre-installed solar radiation sensor and a ultra-violet (UV) radiation sensor. Temperature and humidity sensors are mounted in a Passive radiation shield to minimize the impact of solar radiation on sensor readings. The Anemometer measures wind speed and direction and can be installed adjacent to the iss or apart from it. On an iss Plus, the additional solar and UV sensors are mounted next to the rain collector cone. Separate solar and UV sensors are available to upgrade a standard iss. The sensor interface module (SIM) contains the “brains” of the iss and the radio transmitter. The SIM is located on the front of the radiation shield in the SIM box. The SIM collects outside weather data from the iss sensors and then transmits the data to your Vantage Pro2 console, Vantage Vue console, weather envoy8x, or weather envoy which are sold separately. Available for sale in the United States and Canada only.