See the inlaid daily chart, the index halted its corrective rally almost exactly on the 'middle' trendline of the equi-distance parallel channel. Since then the index came cracking with vengeance. Its resumption of bearish trend, started since cycle top of 3906. On the downside 1600-1650 is where the bulls will try to defend themselves, but it could be a temporary respite. In short, as long as STI trades <1860>
On the long term (monthly) charts, the support line has almost lost its relevance and now giving way to the bears to push the index lower, may be towards Mar 2003 lows.