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SALES SERVICE REVENUE, NET AND ACCOUNTS RECEIVABLE (Narrative) (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2021
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2021
USD ($)
segment
Sep. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
SALES SERVICE REVENUE, NET AND ACCOUNTS RECEIVABLE [Abstract]          
Number of segments | segment     1    
Revenue from sales-type leases $ 100,000 $ 0 $ 100,000 $ 0  
Deferred revenue $ 148,000   $ 148,000   $ 6,000