> Radio firmware and state machines have always had weird bugs, and even when it conforms to standards (some of which are extremely interpretable), does very we

> Radio firmware and state machines have always had weird bugs, and even when it conforms to standards (some of which are extremely interpretable), does very weird things in the real world. Pre-smartphone, being able to update phone and radio firmware was extremely rare, so it was common for the networks instead to implement workarounds on a manufacturer or handset basis. Having a hardware ID that identified this was extremely useful Now that it’s common for devices to be updated regularly, they will typically send an extended form of the IMEI to the network called the IMEISV, which is the same as the IMEI except the final check digit is replaced with a two-digit code indicating the current software version (SV = Software Version).