The circuit is light seeking; it will follow a flashlight around a darkened room. A pair of photocells determine the direction in which the robot will move. Each photocell is connected to an op amp configured as a comparator. When sufticient light falls on photocell R2, the voltage at the inverting input (pin 6) of IC1-a will fall below the voltage at the non-inverting input (pin 5), so the output of the comparator will go high, and transistors Q1 and Q2 will turn on.
