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Inventories (Tables)
3 Months Ended
Mar. 31, 2020
Inventory Disclosure [Abstract]  
Inventory components

Inventories consist principally of raw materials and sub-assemblies, which are stated at the lower of cost (first-in, first-out) or market. Inventories at March 31, 2020 and December 31, 2019 were as follows:

 

   March 31,  December 31,
   2020  2019
Raw materials and sub-assemblies  $3,706,834   $3,767,588 
Finished goods   235,524    241,681 
Inventory reserves   (647,639)   (830,361)
Inventory, net  $3,294,719  $3,178,908