Heat Pumps and Electric Heating - Defrost For Ducane?

Conserning A Ducane H/p Model #sh10b30p, Which Becomes A Winter Wonderland When Ambient Temp Drops Below 40 Deg.
I Noticed A Canister With Two Wires That Resembles A Tiny Turn Signal Flasher On One Of The 4 Small Tubes Entering The Evaporator / Condenser. Demand Defrost???? Assumeing This Is A Temp Sensor, Can I Get This Item In Different Temp Values? Heat Strips Sure Can Use A Lot Of Elec.
A/c Works Great. Any Input Will Be Appreciated.

I have the same unit that I installed about 6 months ago.....first couple of cold mornings my unit was frozen. The factory defrost cycle is set to 90 minutes so I changed it to 60 minutes and the unit doesn't frost up near as much. Still contemplating going to a 30 minute defrost cycle as our temps in Maryland are holding at 15'F to 40'F this time of year. I've also always used the setback feature on my t/stat but have found this unit doesn't seem to want to keep up with demand so I've since set my t/stat and left it alone.

Just food for thought. I too have a Ducane. Compared to your neighbors, where is your outside unit located? Mine is on the cold side of the house while my neighbors units are on the oposite side. So much for my builder knowing which side to place mine on. Oh, by the way, I live fairly close to you...Winchester, VA