I have a 1950s low-voltage lighting system, as described in this question, and while tearing out the wires in the basement, I somehow disabled the entire system. By trial and error, I discovered that the system works again throughout the whole house if I bypass the component circled in red and labeled A. This is only one of the transformers in the system, but it appears that they are all connected somehow. I added the white wire circled in green and labeled B to bypass component A, and now everything works.
The questions are...
- What is component A?
- Why is it blocking current?
- Is it probably safe to bypass it the way that I have? If not, what should I do?