Accrued expenses: (Details) (USD $)	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Accrued expenses:
Warranty	$ 850,499	$ 955,549	$ 933,270
Salary, benefits and payroll taxes	531,862	476,152
Professional fees	330,858	352,559
Income taxes payable	132,980	152,658
Materials on order	43,374	89,392
Other	834,239	525,079
Total	$ 2,723,812	$ 2,551,389