1) As Lao Dao pointed out, VISN is not a stock to have to begin with.  The drop was caused by unexpected weaker FA.  So that is why I like the people at this website as FA is always the first cut on selection of stocks. 

2) When $5.00 didn't hold, testing $4.80 was a sure thing.  So watch the price movement near $4.80.  A V-shape could prove a temporal bottom for DT.

3) For swing trade, still need to wait until a second touch around $4.80 and hold if it touches back next day.  Best entry should be above $5.00, not below $5.00.

4) My mistake.  I planned to enter the position for swing trade and looking for 10% bounce back to $5.40 area.  I bought at the wrong price and wrong time; and the stoploss was set a little too close to the all-time low. 

5) Should not be on the long side for DT especially for today.  Again, it is not a good short candidate after a drop of 40%.   

The mistake cost me a dinner (with trading fees).  I made substantially more from other tradings today.  But this one is unique for learning.  I will keep it in my trading notes with all the charts (long term, short term, and technical indicators).