Help Identifying Mystery Device

[ixu]

@dylan.christopherson just posted some (likely) relevant info for you here:

@dylan.christopherson

My experience with furnace blowers has shown that if you are using the fan as a circulator (fan ON) and the the unit receives a call for either heating or cooling it will first stop the fan and the initiate either the heating or cooling sequence. If cooling, the fan may only stop for a couple seconds. For [gas] heating, the fan will remain off a bit longer until the main heat exchanger gets up to temp.