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MAJOR CUSTOMERS (Details) - Customer
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Revenue | Verizon Communications Inc.          
MAJOR CUSTOMERS          
Concentration risk, percentage 16.00% 15.00% 15.00% 17.00%  
Revenue | AT&T Inc.          
MAJOR CUSTOMERS          
Concentration risk, percentage   16.00%   12.00%  
Accounts receivable balance          
MAJOR CUSTOMERS          
Concentration risk, percentage     15.00%   22.00%