valve called a flame failure device for gas hobs (cooktops) and ovens. The safety valve depends on a thermocouple that sends a signal to the valve to stay open. Although most modern gas stoves have electronic ignition, many households have gas cooking ranges and ovens that need to be lit with a flame. Electric ignition stoves use electric sparks to ignite the surface burners. This is the "clicking sound" audible just before the burner actually lights. The sparks are initiated by turning the gas burner knob to a position typically labeled "LITE" or by pressing the 'ignition' button. Once the burner lights, the knob is turned further to modulate the flame size. Auto reignition is an elegant refinement: the user need not know or understand the wait-then-turn sequence. They simply turn the burner knob to the desired flame size and the sparking is turned off automatically when the flame lights. Auto reignition also provides a safety feature: the flame will be automatically reignited if the flame goes out while the gas is still on—for example by a gust of wind. If the power fails, surface burners must be manually match-lit. Electric ignition for ovens uses a "hot surface" or "glow bar" ignitor. Basically it is a heating element that heats up to gas's ignition temperature. A sensor detects when the glow bar is hot enough and opens the gas valve. Also stoves with electric ignition must be connected with gas protection mechanisms such as gas control breaker. Because of this many manufacturers supply stoves without electricity plug. Features Burner heat One of the important properties of a gas stove is the heat emitted by the burners. Burner heat is typically specified in terms of kilowatts or British Thermal Units per hour and is directly based on the gas consumption rather than heat absorbed by pans. Often, a gas stove will have burners with different heat output ratings. For example, a gas cooktop may have a high output burner, often in the range , and a mixture of medium output burners, 1.5 to 3 kW, and low output burners, 1 kW or less. The high output burner is suitable for boiling a large pot of water quickly, sautéing and searing, while the low output burners are good for simmering. Some high-end cooktop models provide higher range of heat and heavy-duty burners that can go up to or even more. These may