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Inventories (Tables)
3 Months Ended
Mar. 31, 2021
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, 2021 and December 31, 2020 were as follows:

 

    March 31,   December 31,
    2021   2020
Raw materials and sub-assemblies   $ 4,087,028     $ 3,642,377  
Finished goods     393,831       281,104  
Inventory reserves     (755,943     (727,639
Inventory, net   $ 3,724,916     $ 3,195,842