You feed it a colour bar pattern hit adjust and wait for it to stabilise.
This is from a 4 year old post on a newsgroup from a guy called plisken who I won't credit as he was actually me!
I'm assuming you have a panasonic TV?
DVCO (take a guess at deflection voltage cut-off/correction??) : leave it
alone you need a PAL colour bar for it to auto adjust to. (more info to
follow ) *UPDATED* service manual: Recieve a PAL colourbar pattern. FOR DVCO
alignment press blue button wait until the colours are changing slowly and
press "STR"
(in practice the" colour changing slowly bit means that the numbers have
stabilised it takes about 10 secs. The value it satbilises to can vary
depending on the input and the source material ie I get slightly different
values using the PAL colourbar on that free total dvd disc than I do with
the Video Essentials one. Personaly I trust the VE one as its full bandwidth
the total dvd disc looks like its come off a composite source. I use this to
cal the dvd player via RGB. For my digibox as I've yet to find a transmitted
colour bar the discovery kids and wings ident works well: all you need is
something that contains the full gammet of displayable colour values and
this comes close.
Panasonic advised me to do this to correct some (very minor)flickering in
peak white areas via RGB It didn't really correct this fully and I suspect
this procedure fixes a flickering black line problem instead. It is a fairly
harmless procedure if you stick to the recommendations though so give it a
go. I suspect it controls the deflection interval between two scanlines for
a given field hence the black line problem when its incorrect: could be
wrong though)