Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 18,562	$ 22,933	$ 24,519	$ 22,185	$ 20,570	$ 21,933	$ 21,770	$ 22,265	$ 88,199	$ 86,538	$ 90,564
Cost of sales	8,599	10,819	12,560	10,641	10,977	10,870	10,584	11,506	42,619	43,937	43,496
Gross profit	9,963	12,114	11,959	11,544	9,593	11,063	11,186	10,759	45,580	42,601	47,068
Operating expenses:
Product development and engineering	5,112	4,901	5,310	5,125	4,803	5,060	5,392	5,578	20,448	20,833	19,381
Selling, general and administrative	6,570	7,281	7,379	7,736	8,394	8,185	8,624	9,877	28,966	35,080	36,696
Total operating expenses	11,682	12,182	12,689	12,861	13,197	13,245	14,016	15,455	49,414	55,913	56,077
Operating loss	(1,719)	(68)	(730)	(1,317)	(3,604)	(2,182)	(2,830)	(4,696)	(3,834)	(13,312)	(9,009)
Interest expense	(8)	(11)	(22)	(14)	29	(39)	20	(34)
Other income (loss), net	(21)	188	(296)	81	275	350	(29)	75	(48)	671	(214)
Income (loss) from continuing operations before provision for income taxes	(1,748)	109	(1,048)	(1,250)	(3,300)	(1,871)	(2,839)	(4,655)	(3,937)	(12,665)	(9,392)
Provision for income taxes	2,783	(39)	77	50	1,695	71	135	(28)	2,871	1,873	(34)
Income (loss) from continuing operations	(4,531)	148	(1,125)	(1,300)	(4,995)	(1,942)	(2,974)	(4,627)	(6,808)	(14,538)	(9,358)
(Income) loss from discontinued operations, net of taxes	(2,185)	738	844	232	364	902	707	410	(371)	2,383	2,536
Net loss	$ (6,716)	$ 886	$ (281)	$ (1,068)	$ (4,631)	$ (1,040)	$ (2,267)	$ (4,217)	$ (7,179)	$ (12,155)	$ (6,822)
Net income (loss) per share — basic
From continuing operations (usd per share)	$ (0.65)	$ 0.02	$ (0.16)	$ (0.18)	$ (0.68)	$ (0.26)	$ (0.40)	$ (0.64)	$ (0.97)	$ (1.98)	$ (1.25)
From discontinued operations (usd per share)	(0.31)	0.11	0.12	0.03	0.05	0.12	0.10	0.06	(0.05)	0.32	0.34
Net loss per share — basic (usd per share)	(0.96)	0.13	(0.04)	(0.15)	(0.63)	(0.14)	(0.30)	(0.58)	(1.02)	(1.66)	(0.91)
Net Income (loss) per share — diluted
From continuing operations (usd per share)	(0.65)	0.02	(0.16)	(0.18)	(0.68)	(0.26)	(0.40)	(0.64)	(0.97)	(1.98)	(1.25)
From discontinued operations (usd per share)	(0.31)	0.11	0.12	0.03	0.05	0.12	0.10	0.06	(0.05)	0.32	0.34
Net loss per share — diluted (usd per share)	$ (0.96)	$ 0.13	$ (0.04)	$ (0.15)	$ (0.63)	$ (0.14)	$ (0.30)	$ (0.58)	$ (1.02)	$ (1.66)	$ (0.91)
Basic (shares)	6,980	6,978	6,988	7,131	7,368	7,362	7,360	7,283	7,019	7,344	7,484
Diluted (shares)	6,980	7,014	6,988	7,131	7,368	7,362	7,360	7,283	7,019	7,344	7,484
increase in provision for income taxes related to increase in valuation allowance on deferred tax assets	$ 2,600				$ 1,900