The objective of the workshop is to build a module to detect a train as it interrupts a laser beam across the track.

While the laser beam is interrupted, one of the module’s outputs goes from +5V to 0V while another output goes from 0V to +5V. If you fit an optional link, the outputs are held in these altered states for 10 seconds after the beam is restored. After 10 seconds, the outputs revert back to their normal states. This provides various options for the module’s use. The picture shows a test setup for the module. A laser diode head is shown at the near side of the image, with a detector at the other side of the track.