how to lock center diff?? (and thanx:)

[ASh <ASh@vilks.cpk.lv>]

Hello!

Everybody's talking about how great handling is when center diff is locked
and so on, but HOW do you do it? In 92' 100 quattro there's only a swich
for locking rear diff... Or am I wrong? 
And if there is no swich, does it mean, that the center diff locks somehow
automatically?

P.S. Thanx for all explanations about UrQ motor modifications:)

WBR, 
Armands
84' 100 CD Avant.
Looking for: 92'100 q

WBR,
Armands