CONDENSED CONSOLIDATED STATEMENTS OF INCOME (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CONDENSED CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Net sales	$ 10,247	$ 11,550
Cost of sales	5,329	5,464
Gross profit	4,918	6,086
Operating expenses:
Engineering, design and product development	1,385	1,165
Selling and marketing	2,208	1,854
General and administrative	2,620	2,290
Operating expenses	6,213	5,309
Operating income	(1,295)	777
Interest and other income (expense):
Interest, net	3	(6)
Other, net	(165)	90
Interest and other income (expense)	(162)	84
Income before income taxes	(1,457)	861
Income tax (benefit) provision	(465)	115
Net income	$ (992)	$ 746
Net income per common share:
Basic (in dollars per share)	$ (0.13)	$ 0.10
Diluted (in dollars per share)	$ (0.13)	$ 0.10
Shares used in per-share calculation:
Basic (in shares)	7,507	7,461
Diluted (in shares)	7,507	7,619
Dividends declared and paid per common share (in dollars per share)	$ 0	$ 0