The EURISII electronic heat cost allocator (EHCA) is available as a 1-sensor and 2-sensor device and can be optionally supplied with an optical and/or radio interface. The wM-BUS protocol according to DIN EN 13757-4 in T1 or S1 mode is used for radio communication. The transmitted data can be encrypted with AES128 according to the OMS standard. The 1-sensor version of the ECA measures the temperature of the radiator surface in the range of 20-110°C. The radiator temperature is then used with a fixed reference temperature of 20°C to calculate a consumption value. The 2-sensor version additionally measures the room temperature, and consumption is calculated using the temperature difference. Therefore, these devices are more accurate and even less susceptible to tampering. Various functions are also implemented to prevent cold metering in summer. For self-reading of consumption values by the user, a check digit can be displayed to verify the validity of the reading (postcard reading).