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Inventories (Tables)
6 Months Ended
Jun. 30, 2019
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 June 30, 2019 and December 31, 2018 were as follows:

 

   June 30,  December 31,
   2019  2018
Raw materials and sub-assemblies   $3,118,418   $2,785,154 
Finished goods    145,076    335,335 
Inventory reserves    (868,161)   (848,161)
Inventories, net   $2,395,333   $2,272,328