There is one cable with exposed wires. A voltage tester does not detect anything. Another cable goes into a junction box for the doorbell transformer. The cable in the junction box also has no power.
How can I troubleshoot the two cables with no power? All the breakers in the circuit box are on. Do I need a remote continuity tester? Is that safe to use at the circuit box?
Edit: this is the cable running into the junction box. The other cable with exposed wire is not pictured.