Note 9 - Warranty (Tables)
 9 Months Ended
Jan. 31, 2014
Product Warranties Disclosures [Abstract]  
Schedule of Product Warranty Liability [Table Text Block]
   
Nine Months Ended January 31,
 
   
2014
   
2013
 
Warranty reserve balance at beginning of period
  $ 90     $ 163  
Expense accrued, including adjustments
    92       (3 )
Warranty costs incurred
    (67 )     (62 )
Warranty reserve balance at end of period
  $ 115     $ 98