CONDENSED CONSOLIDATED BALANCE SHEETS Parenthetical (USD $)	Jul. 31, 2011	Apr. 30, 2011
CURRENT ASSETS:
Accounts receivable, allowance for doubtful accounts	$ 73,886	$ 146,502
Inventories, obsolete	1,792,681	1,792,681
SUPPLEMENTAL TYPE CERTIFICATES, accumulated amortization	2,473,753	2,464,183
Accumulated amortization other assets	321,914	292,465
STOCKHOLDERS' EQUITY
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	100,000,000	100,000,000
Common stock, issued (in shares)	57,194,262	57,194,262
Common stock, owed but not issued (in shares)	278,573	278,573
Treasury stock (in shares)	600,000	600,000
Class A [Member]
STOCKHOLDERS' EQUITY
Preferred stock, par value (in dollars per share)	$ 5	$ 5
Preferred stock, liquidation	100	100
Preferred stock, redemption value	100	100
Class B [Member]
STOCKHOLDERS' EQUITY
Preferred stock, par value (in dollars per share)	$ 5	$ 5
Preferred stock, liquidation	1,000	1,000
Preferred stock, redemption value	$ 1,000	$ 1,000
Class A and B [Member]
STOCKHOLDERS' EQUITY
Preferred stock, authorized (in shares)	50,000,000	50,000,000