Magnetic window sensors in alaram mode...how to troubleshoot?

I have a hard wired system, a DCS system. A zone consisting of window sensors shows it's in alarm mode...that is that a contact is open somewhere. I've checked all the windows, the wired sensor, the magnet, etc. However, I don't know how to check the circuitry, that is if a wired sensor is getting/sending a signal to the processor box. Does anyone know how to check if the wired sensors are connected to the processor signal? I think I may have a broken (or chewed through by a varmint) wire.