Income Taxes - Tax Effects of Temporary Differences and Carry-Forwards (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets [Abstract]
Inventory reserve	$ 301,000	$ 325,000
Fixed assets	0	0
Other reserves and accruals	207,000	133,000
Stock-based compensation	23,000	18,000
Other	0	0
Tax credit carry-forwards	1,966,000	2,284,000
Federal tax loss carry-forwards	1,980,000	2,380,000
State tax loss carry-forwards	734,000	657,000
Foreign tax loss carry-forwards	127,000	173,000
Total deferred income taxes	5,338,000	5,970,000
Valuation allowance	(5,097,000)	(5,627,000)
Net deferred tax assets	127,000	173,000
Deferred Tax Liabilities [Abstract]
Inventory reserve	0	0
Fixed assets	90,000	141,000
Other reserves and accruals	0	0
Stock-based compensation	0	0
Other	24,000	29,000
Total deferred income tax liabilities	$ 114,000	$ 170,000