In a preferred embodiment, the control circuit is for controlling {HEAD ~ current} through {TAIL ~ a resistive load}, for example, a furnace coil 
In a preferred embodiment , the control circuit is for controlling { HEAD ~ current } through { TAIL ~ a resistive load } , for example , a furnace coil
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH