A smoke detector is a device that detects smoke as an indicator of fire. As part of a fire alarm system, commercial smoke detectors send a signal to a fire alarm control panel. Household smoke detectors, also known as smoke alarms, generally emit an audible or visual alarm if multiple devices are interconnected. The control panels on the market range from a small compact type that includes a hooter/siren and can accommodate a few different types of Sensors to a more advanced type that can perform more complex functions such as automatic dialing to a phone, cellular phone, and conveying a pre-recorded message informing about intrusion, in addition to or instead of, local audio visual security alarm.