Today I was in my attic checking out a ventilation issue (which I may post a separate question about). While up there, I noticed this strange electrical box mounted next to the light in the attic. There is low-voltage wire connected to it, running somewhere else. I'm unable to trace it back to it's source due to insulation in the attic. What is this? Please see all pictures at the link below.
It's a transformer (converts from normal household voltage to low voltage.)
Turn off power to that light (i.e. find the breaker that shuts it off) and then try to ring the doorbell.
Certainly that wire appears to be the normal doorbell wire, and doorbells are a very normal thing to be fed off such a transformer.