Many Evenheat kiln designs use a switch called a Low-Medium-High Switch, often abbreviated LMH. This switch allows for 3 heat settings: Low, Medium and High.

This switch should not be confused with the Infinite Switch.

In order to function, the Low/Medium/High switch is connected to a even number of heating elements or circuits, usually two. It's operation is quite simple. In the low position both of the heating elements are connected in series which gives 25% of total power. In the medium position, only one of the two elements see the total applied voltage which then gives 50% power. In the high position, both elements see the total applied voltage which then gives 100% power. It's a perfect, real world application of the series / parallel relationship.

It should be noted that the Low/Medium/High switch also contains an Off setting.
 

Does the LMH Switch Shut the Kiln Off at the End of the Firing?

No. The Low/Medium/High Switch is a manually controlled switch. It stays where you set it.