Video scrambling technique, used with horizontal blanking inversion, active video inversion, or both. In split sync, the horizontal sync pulse is “split,” with the second half of the pulse at +100 IRE instead of the standard –40 IRE. Depending on the scrambling mode, either the entire horizontal blanking interval is inverted about the +30 IRE axis, the active video (after colour burst and until the beginning of front porch blanking) is inverted about the +30 IRE axis, both are inverted, or neither is inverted. By splitting the horizontal sync pulse, a reference of both –40 IRE and +100 IRE is available to the descrambler. Since a portion of the horizontal sync is still at –40 IRE, some sync separators may still lock on the shortened horizontal sync pulses. However, the timing circuits that look for colour burst a fixed interval after the beginning of horizontal sync may be confused. In addition, if the active video is inverted, some video information may fall below 0 IRE, possibly confusing sync detector circuits. The burst is always present at the correct frequency and timing, however, the phase is shifted 180 degrees when the horizontal blanking interval is inverted.