Above is a temperature sensor made up of different circuits called modules. When the thermistor is warmed its resistance falls, allowing current to flow from positive 9 volts to 0 volts. In turn, current flows from the temperature module to the transistor module triggering the transistor. The bulb module then lights.

However, there is a problem - the bulb flickers on and off. Redesign the transistor module to ensure that the bulb is constantly alight.

Explain how the three modules work together.