DEFA Termini cabin heaters use a PTC (PTC = Positive heat coefficient thermistor) heating element that automatically adjusts the output power according to the temperature at the air inlet. Every 20°C temperature increase causes a 10% power decrease, and as the cabin temperature increases, the electricity consumption gradually decreases. The cabin heater has automatic overtemperature protection.

DEFA Termini cabin heaters have been tested and approved by EN 60335-1 and EN 50408 Safety Standards.