Business Description And Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) reporting_unit	Dec. 31, 2017 USD ($)
Business Description And Significant Accounting Policies [Line Items]
Cash held in foreign accounts	$ 362,000	$ 187,000
Demonstration inventory useful life (in months)	36 months
Accumulated amortization for demonstration inventories	$ 14,174,000	13,469,000
Number of reporting units | reporting_unit	1
Goodwill impairment	$ 0	0
Maximum period in which accounts receivable become due	90 days
Recognized foreign currency transactions gain (loss)	$ 72,000	(177,000)
Advertising expense	$ 314,000	400,000
Minimum [Member]
Business Description And Significant Accounting Policies [Line Items]
Estimated useful lives of the equipment and leasehold improvements (in years)	1 year
Warranty period	1 year
Warranty period (in years)	1 year
Maximum [Member]
Business Description And Significant Accounting Policies [Line Items]
Estimated useful lives of the equipment and leasehold improvements (in years)	7 years
Warranty period	3 years
Warranty period (in years)	3 years
Demonstration Inventories [Member]
Business Description And Significant Accounting Policies [Line Items]
Accumulated amortization for demonstration inventories	$ 1,900,000	1,500,000
Leasehold Improvements [Member] | Minimum [Member]
Business Description And Significant Accounting Policies [Line Items]
Estimated useful lives of the equipment and leasehold improvements (in years)	1 year
Leasehold Improvements [Member] | Maximum [Member]
Business Description And Significant Accounting Policies [Line Items]
Estimated useful lives of the equipment and leasehold improvements (in years)	8 years
Key Tronic Corporation [Member] | Affiliated Entity [Member]
Business Description And Significant Accounting Policies [Line Items]
Sales to related party	$ 13,000	$ 133,000