We're currently looking to replace our wired doorbell, but before doing so I wanted to understand the existing wiring - unfortunately I don't!
We have a transformer next to our consumer unit supplying 12V AC to the circuit, and a single push button outside the front door (which only has a single pair coming to it). Each of these accounts for 1 pair of twin wires arriving into the chime - why might there be a third pair?
Each of the pairs has one wire commoned together in the wire nut. From what I can tell, it seems the transformer supply is connected to the T3 terminal, with the other two on 0F.
I'm intending to replace this like-for-like, just with a nicer looking chime, so I could just reconnect everything as-is on the new one, but I'd like to know what this other wire is for! Does this imply that we might have another push button somewhere?
If I separate out the two non-transformer leads, and try one at a time to figure out which is the actual push button, am I probably better off leaving the other pair disconnected, since we have no idea where it might be going?