CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
CONSOLIDATED STATEMENTS OF OPERATIONS
Net sales	$ 4,529,000	$ 3,702,000	$ 13,742,000	$ 11,657,000
Cost of goods sold	3,091,000	2,657,000	9,686,000	7,920,000
Gross profit	1,438,000	1,045,000	4,056,000	3,737,000
Operating expenses:
Engineering	267,000	215,000	806,000	662,000
Selling, general and administrative	1,140,000	1,146,000	3,783,000	3,353,000
Operating expenses	1,407,000	1,361,000	4,589,000	4,015,000
Earnings (loss) from operations	31,000	(316,000)	(533,000)	(278,000)
Other expense:
Interest expense, net	28,000	5,000	53,000	16,000
Earnings (loss) before provision (credit) for income taxes	3,000	(321,000)	(586,000)	(294,000)
Provision (benefit) for income taxes	310,000	(130,000)	85,000	(118,000)
Net earnings (loss)	$ (307,000)	$ (191,000)	$ (671,000)	$ (176,000)
Basic earnings (loss) per share	$ (0.06)	$ (0.04)	$ (0.13)	$ (0.03)