When beacons are used to determine occupancy, the beacons may use trilateration to determine occupancy. Bluetooth beacons may have a Received Signal Strength Indicator (RSSI) value. This RSSI value is the signal strength of the beacon at a known distance. The personal electronic device (PED) carried by a person (or object) picks up the beacon and can determine its signal strength at the personal electronic device. The personal electronic device can then broadcast this information to the controller 110 using, e.g., a network. An approximation of the PED location can be determined using the known output signal strength of the beacon and the signal strength at the PED.

The sensor 125, 220 or the controller 110 may determine the location of one or more people in the building based on their personal electronic device wireless signal 210, 215. The controller then may use a modifier 140 to change state location in the defined space 105 based on the number of noticed people. The controller may use its ability to control an HVAC system to raise or lower the temperature, turn off a piece of equipment to lower noise in the space, change the humidity, etc.