Hex Bugs are tiny robots that react to sound and touch. To do this, they use sensors that act like ears and whiskers. The bug's brain is a printed circuit board (PCB), which carries instructions from the sensors and electricity from the batteries to an electric motor.

This bug's ear is a microphone. The microphone translates the pressure from sound waves into electrical impulses. The circuitry on the PCB detects the impulses and sends a signal to the motor, telling it to change direction so the bug can back up.

A Hex Bug's antennae are similar to a cat's whiskers. Cats use their whiskers to help them decide whether they can fit through narrow spaces. If the whiskers touch the edges, the space is too narrow. Springs allow the robot to do the same thing.

At the base of each antenna, a small spring winds around a plastic insulator. This insulator keeps the spring away from a metal electrode inside. But when the antenna touches an object, the spring bends and touches the electrode, completing a circuit. The bug's circuitry tells the motor to change direction, and the bug backs up.

The robot's motor is tiny, and it turns a very small gear. This gear connects to other gears, which carry the motor's movement to the bug's middle legs. The middle legs connect to the front and back legs with small plastic bars. The middle legs push and pull the bars, which causes the front and back legs to move.

None of this happens unless the Hex Bug's switch is in the "on" position. The switch slides back and forth, carrying a small piece of metal with it. When the piece of metal is in the right place, it touches two electrodes. This completes the circuit between the batteries and the rest of the bug.

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When Hex Bugs back up, a simple clutch keeps the left legs from moving. Both middle legs attach to shafts. The right shaft fits through a spiral, and the left connects to a housing. When the motor turns, the spiral's pointed end fits into a notch in the housing. The housing turns, moving the left legs. When the motor reverses, the point slips past the notch, so the left legs stay still.