If you've ever moved into a new house or apartment, the first few months are full of learning things about your new home. Maybe there are strange creaks in the middle of the night, or perhaps the water pipes shake if the shower tap isn't at full strength. With the change of seasons comes another set of new discoveries: If you set the thermostat at 68 degrees, will it actually be 68 degrees in your living room? The piece of equipment that does this job – or not, as you may discover – is the thermostat. It measures the temperature in the room and then sends a signal to the heating system to adjust if needed until the temperature matches the level you set.

To make sure that agile strategy efforts stay on track, we use a feedback loop. This idea comes from industrial control systems, in which the loop helps maintain the stability of the system. The thermostat provides the feedback on the heating system, for example. A system without a feedback loop can spin out of control.


A room thermostat monitors temperature more or less continuously. It's not taking any other information into account; for example, when spring comes around, we need the heating system less frequently, but the thermostat doesn't know it's spring – if it did, perhaps it would have already told the heating system to start its adjustment. Instead, the thermostat just keeps checking the room temperature and sends the data on. Each ...

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