This document discusses phase shifts in digital TV signals and I/Q vectors. It explains that I/Q vectors can become inverted, swapping the in-phase and quadrature components of the signal. This causes some symbol pairs, like 10 and 01, to be reversed at the receiver. However, receivers can detect this automatically by looking for the synchronization byte which is fixed in the transport stream packets. Reversing the I/Q inversion at the receiver corrects the signal again.