There are in fact only 3 active connections to the optical sensor. 2 & 5 are +5V & GND respectively, 6 is the output. It is not in fact a pulse, in that there is no control of the shape of the output using (say) a Schmitt trigger. I am measuring pin 6 at within 3 mV of GND in darkness and 35 mV of VCC in reasonably bright light. The output goes to an acceptable ‘high’ state long before the LED on the rear of the sensor lights up.