This is an Infrared Transmitter and receiver which together make up a photoelectric sensor. The sensor has a long detection distance, and has less interference by visible light because it uses modulated Infrared light. This sensor has a screwdriver adjustment to set the detected distance, then gives a digital output when it senses something within that range. This sensor does not return a distance VALUE. See the photo on right:

Connections are:

• RED: +5 VDC
• GREEN: Ground
• YELLOW: Output: Open Collector Pulldown: Use 10K Pullup resistor to +5V
• Electrical Characteristics

Power Supply:                                   5VDC
supply current DC                              <25mA
maximum load current                       100mA (Open-collector NPN pulldown output)
response time                                     <2ms
Diameter:                                           17MM
pointing angle:                                    ≤ 15 °, effective from 3-80CM Adjustable
detection of objects:                            transparent or opaque
working environment temperature:     -25℃+55℃
Case Material:                                     Plastic
Lead Length:                                       65CM

Datasheet:

        http://www.electronicaestudio.com/docs/SHT-015d.pdf