The 542-2204-02 is a replacement part for the Concord Express alarm system. It is a two-zone expansion module and provides additional burglary protection by adding two additional, independent zones to the system. Each zone supports up to 12 contact devices that can be connected to your system. It can serve as a traditional two-stage alarm with connected devices such as motion detectors, door and window contacts, vibration sensors, and more. In addition, it can also be used to expand automation capabilities for your Concord Express system like controlling lights, shades, locks, and more.