bluetooth uses

Uses:
Bluetooth is a standard and communications protocol primarily designed for low power consumption, with a short range (power-class-dependent: 1 METER, 10 meters, 100 meters) based on low-cost TRANSCIEVER MICROCHIPin each device.

Bluetooth enables these devices to communicate with each other when they are in range. The devices use a radio communications system, so they do not have to be in line of sight of each other, and can even be in other rooms, as long as the received transmission is powerful enough.
Class
Maximum Permitted Power mW(dBm)
Range(approximate)
Class 1
100 mW (20 dBm)
~100 meters
Class 2
2.5 mW (4 dBm)
~10 meters
Class 3
1 mW (0 dBm)
~1 meter
It has to be noted that in most cases the effective range of class 2 devices is extended if they connect to a class 1 transceiver, compared to pure class 2 network. This is accomplished by higher sensitivity and transmitter power of the Class 1 device. The higher transmitter power of Class 1 device allows higher power to be received by the Class 2 device. Furthermore, higher sensitivity of Class 1 device allows reception of much lower transmitted power of the Class 2 devices. Thus, allowing operation of Class 2 devices at much higher distances.