Professional gear and cables are generally balanced, meaning that the signal is carried on three wires within the cable, a high, a low, and a ground. The high and low carry the identical signal, but 180 degrees out of idea of a balanced line works like this. Since some audio signals can be fairly week, like the low-level signal from a microphone, the cable could be susceptible to picking up electromagnetic fields. If and when this happens, the signal strength of the electromagnetic field (be it hum or RF) will be equal on both the high and the low. When the cable terminates at the console, a transformer reverses the phase of the low side, including any hum or RF that it picked up after the microphone. The positive hum or RF on the high side is added to the equal but negative hum or RF on the low side, and like matter and anti-matter, they completely cancel out. The actual signal from the microphone, which was out of phase on the cable to begin with, is added together in phase and becomes twice as loud (approximately 6 dB).Contrast this to an unbalanced line that only has a high plus analogy could be made that the balanced line is like a dual coil humbucker guitar pickup versus an unbalanced single coil pickup, with the same results.