The Vitus 979 frame was one of the best road frame for the middle of 80ies.
It was impossible to weld "duralumin". So the french engineers sticked the tubes on "connection". It's a very old technology, seen on old road bikes (after WW2 !), and this technology was first used on all aluminium bike until the beginning of 90ies (vitus, alan, trek, giant, reflexâ€¦) and for the first carbon frame with aluminium connection(alan, vitus, trek, look, TVTâ€¦)
The bikes were very confortable because of the non oversized diameter of the aluminium tubes. Aluminium is not stiff, the big diameter of the tube gives more stiff frame. It would be the same thing with steel but the frame would be too heavy.
The frame was built until the middle of 90ies : it was a confortable cheap frame.
You have the same frame but with the front made with 3 carbon-graphite tubes