Smoke Detectors are placed high on the walls and ceilings. They are on at all times.
Heat Detectors are also placed high on the walls and ceiling, they sense the rapid rise in heat.
Carbon Monoxide Detectors are used to sense a fatal amount of deadly carbon monoxide.
Manual Pull Stations are used to alert the entire building of a fire condition. They are usually placed near exit doors and are placed according to several jurisdictional laws.
(ADA, NFPA, AHJ)
Waterflow Devices are attached to the riser of your sprinkler system in order to alert you and the fire department that water is flowing through your sprinkler system.
Gate Valve Tampers are placed on the stem of the gate valve (on / off switch) of sprinkler system. They are used to alert you that your sprinkler system has been disabled.
High / Low Pressure Sensors are placed on your sprinkler system to let you know if your system is losing pressure, or has too much.