CONDENSED CONSOLIDATED STATEMENTS OF INCOME (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Net sales	$ 14,751	$ 13,596	$ 26,994	$ 27,593
Cost of sales	7,760	7,166	14,141	15,070
Gross profit	6,991	6,430	12,853	12,523
Operating expenses:
Engineering, design and product development	1,183	1,020	2,404	2,013
Selling and marketing	2,079	2,034	3,652	3,706
General and administrative	2,111	2,070	4,323	4,082
Operating expenses	5,373	5,124	10,379	9,801
Operating income	1,618	1,306	2,474	2,722
Interest and other income (expense):
Interest, net	(6)	(8)	(14)	(16)
Other, net	(97)	(2)	(87)	(8)
Interest and other income (expense)	(103)	(10)	(101)	(24)
Income before income taxes	1,515	1,296	2,373	2,698
Income tax provision	305	429	483	888
Net income	$ 1,210	$ 867	$ 1,890	$ 1,810
Net income per common share:
Basic (in dollars per share)	$ 0.16	$ 0.12	$ 0.25	$ 0.24
Diluted (in dollars per share)	$ 0.16	$ 0.12	$ 0.24	$ 0.24
Shares used in per-share calculation:
Basic (in shares)	7,401	7,408	7,467	7,402
Diluted (in shares)	7,660	7,514	7,782	7,469
Dividends declared and paid per common share (in dollars per share)	$ 0.09	$ 0.09	$ 0.18	$ 0.17