Note 8 - Goodwill and Intangibles  | 
6 Months Ended | 
|---|---|
Mar. 31, 2020  | |
| Notes to Financial Statements | |
| Goodwill and Intangible Assets Disclosure [Text Block] | 
 Note  8.  Goodwill and IntangiblesThe Company analyzes its goodwill for impairment annually or at an interim period when events occur or changes in circumstances indicate potential impairment. The result of the analysis performed as of    September 30, 2019  did not  indicate an impairment of goodwill. During the six  months ended  March 31, 2020,  there were no  triggering events that indicate potential impairment exists.The Company capitalizes legal costs incurred to obtain patents. Once accepted by either the U.S. Patent Office or the equivalent office of a foreign country, these legal costs are amortized using the straight-line method over the remaining estimated lives,   not  exceeding 20  years. As of  March 31, 2020,  the Company has 22  patents granted and multiple pending applications both inside and outside the United States.In addition, the Company has various finite lived intangible assets, most of which were acquired as a result of the acquisition of the active cabinet product line from Calix, Inc. (“Calix”) during fiscal year  
2018.  The Company analyzes its intangible assets for impairment annually or at interim periods when events occur or changes in circumstances indicate potential impairment. The result of the analysis performed as of  September 30, 2019  did not  indicate an impairment of our intangible assets. During the six  months ended  March 31, 2020,  there were no  triggering events that indicate potential impairment exists. |