Bluetooth works by running away from interference sixteen hundred times a second. Every Bluetooth device operates in the 2.4 GHz ISM band, 2.400 to 2.4835 GHz. It is unlicensed, which means it is crowded. Wi-Fi is there. Microwave ovens leak there. Baby monitors, cordless phones and Zigbee sensors share the same spectrum. Rather than fight for a clear channel, Bluetooth refuses to sit still. Classic Bluetooth divides the band into 79 channels of 1 MHz each. The connection hops between them 1600 times per second, changing frequency every 625 microseconds. Both devices follow the same pseudo-random hopping sequence, derived from the clock and address of the device acting as master. To anyone else listening, the transmission is brief noise scattered across the band. To the paired device, it is a coherent conversation. Adaptive Frequency Hopping refines this. The radio maps which channels are congested, usually those occupied by Wi-Fi, and removes them from the sequence entirely. Bluet...