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Note 7 - Agreements, Commitments and Contingencies (Tables)
12 Months Ended
Dec. 31, 2020
Notes Tables  
Schedule of Product Warranty Liability [Table Text Block]
  

2020

  

2019

 

Balance at January 1,

 $813,288  $432,225 

Warranty costs charged to cost of goods sold

  348,241   707,079 

Utilization charges against reserve

  (199,624

)

  (315,556

)

Release of accrual related to expired warranties

  -   - 

Foreign currency effect

  94,708   (10,460

)

Balance at December 31,

 $1,056,613  $813,288