What is this junction

[Aamir]

There is no switch in the air handler closet. I am thinking this is a stand in for the switch. What do you all think. 25 year old house.
See the front and side pictures. A pair of blue and white wires coming out of the wall and going into it..

It is warm to touch when power is coming in. It has a coil thing sticking out.

 

[Aamir]

On further internet lookup, it turns out to be some sort of transformer, hence explaining warm to touch. But there is already a transformer in the air handler board. I'll check if this is for alarm bell.

 

[AC Power]

Yes, it is a transformer. Could be for the doorbell, or someone has "bootlegged" in an HVAC (furnace) control somewhere. If I were you, disconnect it and see if anything dies....sounds simple, I know....but that's what I'd do first.

 

[tafmis]

This looks very dodgy to me - I recommend, for your own safety, that you seek the advice of a registered Sparky!