Skylink M-1 Main Console SkylinkNet Alarm Autmoation System, Wireless Siren for Indoor use, White Works as an additional indoor siren for skylinknet alarm system. Also works as a main unit for the m-series alert/alarm system Sounds the siren when the skylinknet internet hub alarm is activated Works as a m-series alert/alarm main unit, by adding up to 16 sensors and arm/disarm system with a keyfob or keypad Add up to 16 wireless accessories/sensors to the main unit