CONDENSED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Activities:
Net income (loss)	$ (1,096,000)	$ 164,000
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	335,000	287,000
Changes in allowance for doubtful accounts	(3,000)	4,000
Deferred income tax benefit	(214,000)	0
Stock-based compensation expense	138,000	67,000
Accrued interest on held to maturity investments	(13,000)	0
Changes in operating assets and liabilities:
Accounts receivable	2,406,000	2,960,000
Inventories	(25,000)	(184,000)
Income tax receivable	2,000	65,000
Prepaid expenses and other	39,000	39,000
Accounts payable	(1,263,000)	(358,000)
Accrued liabilities	(1,900,000)	(642,000)
Income tax payable	8,000	8,000
Deferred revenue	500,000	299,000
Net cash provided by operating activities	(1,086,000)	2,709,000
Investing Activities:
Purchases of property and equipment	(235,000)	(194,000)
Purchase of investments	(4,981,000)	0
Net cash used in investing activities	(5,216,000)	(194,000)
Financing Activities:
Proceeds from issuance of common stock	108,000	49,000
Net cash used in financing activities	108,000	49,000
Increase (decrease) in cash and cash equivalents	(6,194,000)	2,564,000
Cash and cash equivalents at beginning of period	10,160,000	4,695,000
Cash and cash equivalents at end of period	3,966,000	7,259,000
Non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable	$ 35,000	$ 93,000