A relay is installed so the relay on controll circuit is powered by the low beam circuit, this allows the fog lights to only be ON with low beams and can not be ON with high beams. This is the LAW in most all North America. (std odyssey uses fuse #6 under hood)
The relay controlled curcuit uses key on power supplied through a switch to supply power to the fog lamps. so when switch is OFF the fog lights will not come on, when switch is on fog lights will only come on with low beam lights.
One wire of each lamp gets grounded, other goes to #30 relay pin, #87 relay pin to switch #1 , switch #2 to key power, fused and capable of min 20amps. relay #85 to ground, relay#86 to fuse#6 via add a circuit under hood. Voila Fog lights.
We charge 1.5 hrs in a shop to do this, Parts, wiring are around $50