The PAD-5-MB board has an input designed to connect to an external fire alarm control unit's NAC circuit so that the PAD-5-MB board's NAC circuits can follow the activation of the NAC circuits from an external source. The NAC Follower Input is also used for synchronization for the PAD-5-MB and PAD-5-CLSA boards, so that multiple PAD-5’s can be synchronized together across multiple device loop drivers.