Easy operation. LED 2 digits display of temperature and operation status Floor heating mode with 6 ... 2.SD series: Anti-dirty monothemic heat exchanger, LED display temperature and combustion power, Timely error diagnoses, buzzer alarm, Microcomputer ... digital control 3.SP series: Bithermal heat exchanger, LED display temperature and combustion power, Timely error diagnoses, buzzer alarm, Microcomputer ...