Summary of Significant Accounting Polices - Additional Information (Details)	3 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($)	Dec. 31, 2020 USD ($) Segment Customer shares	Dec. 31, 2019 USD ($) Customer shares
Accounting And Reporting Policies [Line Items]
Depreciation expense		$ 453,000	$ 418,000
Intangible assets carrying value		287,000	362,000
Goodwill		$ 40,000	40,000
Term of warranty		1 year
Accrued warranty expense		$ 21,000	29,000
Research and development costs		$ 2,142,000	2,004,000
Warrants to purchase, common stock | shares		1,051,664
Deferred tax asset, valuation allowance eliminated	$ (3,344,000,000)		(3,344,000,000)
Revenue concentration greater than 10%		$ 31,162,000	31,897,000
Number of identified reportable segments | Segment		2
Re-measurement gain (loss)		$ (95,000)	(13,000)
Revenues [Member] | Customer Concentration Risk [Member] | Defense Contract Manufacturer [Member]
Accounting And Reporting Policies [Line Items]
Revenue concentration greater than 10%		$ 5,324,000	$ 3,187,000
Concentration risk, percentage		17.10%	10.00%
Revenues [Member] | Customer Concentration Risk [Member] | Electronics Contract Manufacturer [Member]
Accounting And Reporting Policies [Line Items]
Revenue concentration greater than 10%		$ 4,351,000	$ 5,522,000
Concentration risk, percentage		14.00%	17.30%
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Accounting And Reporting Policies [Line Items]
Concentration risk, percentage		43.10%	40.00%
Accounts receivable		$ 1,856,000	$ 1,841,000
Number of large customers | Customer		4	4
Options [Member]
Accounting And Reporting Policies [Line Items]
Securities excluded from the diluted earnings per share computation (in shares) | shares		25,000	25,000
ASU 2014-09 [Member]
Accounting And Reporting Policies [Line Items]
Revenue, performance obligation, description of timing		The Company meets these conditions upon the Company’s satisfaction of the performance obligation, usually at the time of shipment to the customer, because control passes to the customer at that time. Our standard terms for customers are net due within 30 days, with a few exceptions, none regularly exceeding 60 days.
Minimum [Member]
Accounting And Reporting Policies [Line Items]
Equity method investment ownership percentage		20.00%
Minimum [Member] | ASU 2014-09 [Member]
Accounting And Reporting Policies [Line Items]
Customer due days		30 days
Minimum [Member] | Buildings and Improvements [Member]
Accounting And Reporting Policies [Line Items]
Property, Plant and Equipment, Useful Life		5 years
Minimum [Member] | Other Fixed Assets [Member]
Accounting And Reporting Policies [Line Items]
Property, Plant and Equipment, Useful Life		3 years
Maximum [Member]
Accounting And Reporting Policies [Line Items]
Equity method investment ownership percentage		50.00%
Estimated useful life of intangible assets		10 years
Maximum [Member] | ASU 2014-09 [Member]
Accounting And Reporting Policies [Line Items]
Customer due days		60 days
Maximum [Member] | Buildings and Improvements [Member]
Accounting And Reporting Policies [Line Items]
Property, Plant and Equipment, Useful Life		35 years
Maximum [Member] | Other Fixed Assets [Member]
Accounting And Reporting Policies [Line Items]
Property, Plant and Equipment, Useful Life		10 years