Strange Transformer

On the same outlet box as the power to my security system is a strange looking transformer. The wire coming out of it doesn't go into the security encasement, but rather trails along my basement and then goes up. I cannot for the life of me figure out what it is. The wire says "temperature control system" on the side, but this could just be whatever wire they used for this. Any ideas? If it is part of the security setup I want to understand what it does.

Doorbell power supply.