can distinguish between light and dark areas and could for instance be used to follow a black line on a white surface.

-   The **sound sensor** can measure noise level and is also able to recognize sound patterns and identify tone differences.

-   The **ultrasonic sensor** can measure distances by emitting ultrasonic sound waves. By sensing the time it takes for these sound waves to bounce of an object and return to the sensor, it can measure distances with a precision of 3 centimeters.

Other standard and non-standard sensors, such as older sensors can also be used by the Lego Mindstorms NXT, but they will not be discussed here. Refer to appendix \[app:extensions\] for a description on how to use percepts from these sensors in *Jason*.

### Sampling data from the sensors

The data provided by the sensors is sent to the extension of the *Jason* framework, so that ${A_{\textsf{Jason}}}$ is able to use the values. The samples from a sensor however tend to be somewhat noisy. This means that to successive samples may be very different, even though the environment has not changed.

The samples are therefore compared to previous values, to see whether they seem reasonable. An easy 