CONDENSED CONSOLIDATED STATEMENTS OF INCOME (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
CONDENSED CONSOLIDATED STATEMENTS OF INCOME (unaudited) [Abstract]
Net sales	$ 11,686	$ 15,838	$ 34,586	$ 42,832
Cost of sales	6,140	7,834	17,250	21,975
Gross profit	5,546	8,004	17,336	20,857
Operating expenses:
Engineering, design and product development	1,048	1,106	3,328	3,510
Selling and marketing	1,947	1,798	5,890	5,450
General and administrative	2,239	1,888	6,720	6,211
Operating expenses	5,234	4,792	15,938	15,171
Operating income	312	3,212	1,398	5,686
Interest and other income (expense):
Interest, net	0	(7)	(13)	(21)
Other, net	(71)	(50)	(123)	(137)
Interest and other income (expense)	(71)	(57)	(136)	(158)
Income before income taxes	241	3,155	1,262	5,528
Income tax provision	(143)	581	(54)	1,064
Net income	$ 384	$ 2,574	$ 1,316	$ 4,464
Net income per common share:
Basic (in dollars per share)	$ 0.05	$ 0.35	$ 0.18	$ 0.60
Diluted (in dollars per share)	$ 0.05	$ 0.33	$ 0.17	$ 0.57
Shares used in per-share calculation:
Basic (in shares)	7,470	7,413	7,464	7,449
Diluted (in shares)	7,753	7,758	7,658	7,774
Dividends declared and paid per common share (in dollars per share)	$ 0.09	$ 0.09	$ 0.27	$ 0.27