An electronic device attached to a kiln (usually an electric kiln). These controllers are usually capable of firing a kiln to a specific schedule and can shut it off at the right time, soak it for a specified period, and cool it down at a controlled rate.
The thermocouple senses the temperature in the kiln chamber and sends that information to the controller. The controller takes the information and compares it to the firing program input by the operator and makes a decision to act or not to act.