Four Style B(Class B)Initiating Device Circuits(IDCs)。 All zones accept two-wire smoke detectors and any normally-open contact devices. One built-in Fire Fighting Ouput. 24-volt operation. Resettable four-wire smoke detector power@500 mA. Non-resettable power@500 mA. One-man walk-test programmable for silent or audible test. Disable/Enable control per IDC. Reverse polarity protection