LA5193 Doorway Beam - how to set up the door beam? Goes off when no-one is there

The LA5193 sits on one side of a doorway, and sends out a beam to a reflector stuck on the other side.

Interrupting the beam makes the unit play a chime. 

How to set up the unit

1. Connect the power adaptor and speaker to the sensor as shown above.
2. Hold the sensor on one side of the doorway in a location where it will not get bumped into. 
3. Have an assistant hold the reflector on the other side of the doorway level with the sensor.
4. Using a laser pointer or laser measure, lay it on the sensor, to see where the beam is going to land.
5. Move the sensor or the reflector around till the red LED in the sensor window lights up.
6. Interrupt the beam with your hand - it should trigger the chime and briefly turn the LED off.
7. Fix the sensor and reflector firmly to the doorway. 

Notes:

• If the beam is aimed slightly away, or the reflector is not 90degrees to the sensor, it won't work.
• If the sensor is left in constant direct sunlight, it may trigger when no-one passes through.
• The sensor needs to be mounted firmly to prevent drift - don't use double-sided tape on its own.
• A glass mirror will also work well as a reflector.