Bluetooth uses electrical signals, UHF radio waves in the ISM band of 2.4-2.485 GHz.
The Bluetooth band is 2400-2483.5MHz (including guard bands). This is the worldwide unlicensed (but not unregulated) 2.4 GHz short-range radio band in the Industrial, Scientific and Medical (ISM) band.
Bluetooth uses frequency hopping technology to split the transmitted data into packets, which are transmitted over each of 79 designated Bluetooth channels. Each channel has a bandwidth of 1 MHz. Bluetooth 4.0 uses 2 MHz spacing and can accommodate 40 channels. The first channel starts at 2402 MHz and continues every 1 MHz to 2480 MHz. with Adaptive Frequency-Hopping (AFH), which is typically 1600 hops per second.
At first, Gaussian frequency-shift keying (GFSK) modulation was the only available modulation scheme. However, Bluetooth 2.0+EDR enables the use of π/4-DQPSK and 8DPSK modulation in compatible devices. Devices running GFSK are said to be able to operate at Basic Rate (BR) with instantaneous rates of up to 1 Mbit/s. The term Enhanced Data Rate (EDR) is used to describe the π/4-DQPSK and 8DPSK schemes, which can be up to 2 and 3 Mbit/s, respectively. In Bluetooth radio technology, the combination of the two modes (BR and EDR) is collectively referred to as "BR/EDR radio.