The bottom of the inner pot install a heat-gathering ring, Can be heated fast but heat dissipated slowly. The steel ring absorbs the heat from the fire when you are cooking. Once the food is aboil, you can cut off the fire source and move the inner pot onto the heat-preservation base.
Then the heat-gathering ring will giving out heat, and keep boiling for 25 minutes without flame. After the food is finish, it will keeping the food in high temperature for long time.