The ADOR has an integral built-in photosensor, so normally, you do not need this external sensor. But if you mount the ADOR inside a dark coop, the external photosensor is needed. It plugs into the ADOR's electronic board and the wire should be run over to the exterior wall of the coop where it can "see" ambient daylight.
NOTE: there are two variants:
1. Standard 4 foot wire
2. Long 12' wire
This "D-type" sensor is the "new" type and is for ADORs later than mid-May 2015. If your ADOR or your replacement board for your ADOR was ordered around May 2015 or later, the sensor type you need is this new "D-Type" sensor.. The OLD Type sensor is not compatible with electronics after May 2015.
Here is the instruction sheet for installing this sensor.