Unless you do purely new construction, you often end up hooking up to existing circuitry in many cases.
What's your criteria for the existing system that you connect to?
Must it meet Code? Must it be new or near new? Must it be "safe"? Do you feel that if you modified it or added to it that you've in essence made it your own?
How do you deal with a call where a part of the existing system has failed?
