Smoke detector 2

Interconnected smoke detectors are either conventional or analog addressable, and are wired up to security alarm systems or fire alarm systems controlled by fire alarm control panels (FACP). These are the most common type of detector, and usually cost a lot more than single-station battery-operated smoke alarms. They exist in most commercial and industrial facilities and other places such as ships and trains, but are also part of some security alarm systems in homes. These detectors don't need to have built in alarms, as alarm systems can be controlled by the connected FACP, which will set off relevant alarms, and can also implement complex functions such as a staged evacuation. [Smoke detector. Wikipedia]