CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 27, 2019	Sep. 28, 2018
Text Block [Abstract]
Sales	$ 5,702	$ 12,200	$ 20,873	$ 28,653
Cost of sales	(4,053)	(7,528)	(13,631)	(18,224)
Gross profit	1,649	4,672	7,242	10,429
Operating expenses:
Selling, general and administrative	(1,615)	(1,640)	(5,632)	(5,125)
Research and development	(723)	(628)	(2,459)	(2,148)
Pension	(57)	(55)	(170)	(163)
Total operating expenses	(2,395)	(2,323)	(8,261)	(7,436)
Operating income (loss)	(746)	2,349	(1,019)	2,993
Other expense, net	(56)	(68)	(204)	(243)
Income (loss) before income tax provision	(802)	2,281	(1,223)	2,750
Income tax provision	0	(30)	(19)	(61)
Net income (loss)	$ (802)	$ 2,251	$ (1,242)	$ 2,689
Net income (loss) per common share -basic	$ (0.07)	$ 0.20	$ (0.11)	$ 0.24
Net income (loss) per common share - diluted	$ (0.07)	$ 0.19	$ (0.11)	$ 0.22
Weighted average common shares outstanding - basic	11,483	11,353	11,457	11,353
Weighted average common shares outstanding - diluted	11,483	12,012	11,457	12,002