CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
CONSOLIDATED STATEMENTS OF OPERATIONS
Net sales	$ 3,702,000	$ 3,622,000	$ 11,657,000	$ 11,831,000
Cost of goods sold	2,657,000	2,443,000	7,920,000	7,879,000
Gross profit	1,045,000	1,179,000	3,737,000	3,952,000
Operating expenses:
Engineering	215,000	195,000	662,000	572,000
Selling, general and administrative	1,146,000	811,000	3,353,000	2,714,000
Operating expenses	1,361,000	1,006,000	4,015,000	3,286,000
Earnings (loss) from operations	(316,000)	173,000	(278,000)	666,000
Other expense:
Interest expense, net	5,000	6,000	16,000	19,000
Earnings (loss) before provision (credit) for income taxes	(321,000)	167,000	(294,000)	647,000
Provision (credit) for income taxes	(130,000)	66,000	(118,000)	251,000
Net earnings (loss)	$ (191,000)	$ 101,000	$ (176,000)	$ 396,000
Basic earnings (loss) per share	$ (0.04)	$ 0.02	$ (0.03)	$ 0.07