Segment Reporting - Segment Reporting Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jan. 04, 2019 carrier	Dec. 27, 2018 carrier
Segment Reporting Information [Line Items]
Number of U.S. wireless carriers | carrier											4	4
Total sales									$ 50,182	$ 55,118
Gross profit	$ 4,356	$ 4,171	$ (439)	$ 3,592	$ 3,671	$ 4,587	$ 3,477	$ 1,723	11,680	13,458
Operating income (loss)									(18,530)	(3,976)
Segment assets	32,683				36,828				32,683	36,828
Operating Segments | Wireless
Segment Reporting Information [Line Items]
Total sales									21,354	22,969
Gross profit									6,580	6,362
Operating income (loss)									(2,842)	(882)
Segment assets	5,324				5,516				5,324	5,516
Operating Segments | Telco
Segment Reporting Information [Line Items]
Total sales										32,204
Gross profit									5,100	7,096
Operating income (loss)									(11,341)	134
Segment assets	12,478				22,619				12,478	22,619
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total sales									(25)	(55)
Segment Reconciling Items
Segment Reporting Information [Line Items]
Segment assets	$ 14,880				$ 8,693				14,880	8,693
Corporate
Segment Reporting Information [Line Items]
Operating income (loss)									$ (4,347)	$ (3,228)