[old_tv_nut]

"Oscillating burst"

A (R-Y) or -(R-Y) component is added to the burst on alternate lines, making its phase plus or minus 45 degrees from the NTSC burst.

As mentioned somewhere here, there was a patent on detecting this in the receiver, but one maker avoided the patent by not using the detector. Instead, they added a button so the user could flip the phase sequence from plus/minus to minus/plus in case it came up wrong at random.