Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 7,228	$ 16,966
Accounts receivable, net of allowances of $26 and $26, respectively	2,502	15
Costs and estimated earnings in excess of billings on uncompleted contracts	258	680
Inventory	4,519	4,541
Other current assets	1,547	1,015
Total current assets	16,054	23,217
Property and equipment, net	2,950	3,251
Restricted cash	435	435
Intangible assets	573	602
Other assets	2,506	2,262
Total assets	22,518	29,767
Current liabilities
Accounts payable	1,989	3,063
Accrued liabilities	6,607	5,864
Deferred revenue		0
Billings on uncompleted contracts in excess of related costs	4	5
Other current liabilities	10,103	10,142
Total current liabilities	18,703	19,074
Deferred revenue, net of current portion		0
Deferred rent, net of current portion	366	302
Other long-term liabilities	163	305
Total liabilities	19,232	19,681
Commitments and contingencies (Note 7)
Shareholders' equity
Preferred stock, par value $0.001; 25,000 shares authorized; zero and zero shares issued and outstanding	0	0
Common stock, par value $0.001; 100,000 shares authorized; 78,613 and 78,597 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	79	79
Additional paid-in capital	529,205	528,873
Accumulated deficit	(525,998)	(518,866)
Total shareholders' equity	3,286	10,086
Total liabilities and shareholders' equity	22,518	29,767
Reconciliation of cash, cash equivalents, and restricted cash balances
Cash and cash equivalents	7,228	16,966
Restricted cash	435	435
Cash, cash equivalents, and restricted cash	$ 7,663	$ 17,401